GIFT  OF 
Author 


THE  EVOLUTION  OE  CLIMATES 


MANSON 


THE  EVOLUTION  OF  CLIMATES 


BY 


MARSDEN  MANSON 


COPYRIGHT,  1922,  BY  MARSDEN  MANSON 


NOTE 

THIS  ESSAY  IS  THE  RESULT  OF 
MORE  EXTENDED  STUDIES  SINCE 
THE  PUBLICATION,  UNDER  THE 
SAME  TITLE,  OF  A  PAPER  IN  THE 
AMERICAN  GEOLOGIST,  VOL.  XXIV, 
AUGUST  1899;  AND  OF  PREVIOUS 
AND  SUBSEQUENT  PAPERS  IN  VAR- 
IOUS PUBLICATIONS  SINCE  1891. 


BALTIMORE,   MD.,   U.   8.   A. 


DeDtcatton 

faoofe  10  Dctncatct)  to 
belobeb  toife,  3ulia  2Diana 


anb  encouragement 
been  a  constant  aid. 


547542 


ACKNOWLEDGMENTS 

To  the  laborers  in  the  fields  of  Glacial  Geology  and  Meteorology 
into  which  the  author  has  ventured,  he  feels  deeply  indebted.  Nearly 
all  of  them  differ  radically  from  the  views  and  conclusions  now 
presented ;  but  no  unanimity  prevails  as  to  the  cause  or  causes  and 
the  conditions  which  have  governed  the  climates  of  the  past.  No 
conclusions  which  have  been  reached  by  those  who  have  attempted 
a  solution  have  been  acceptable.  The  entire  problem  is  therefore 
open  for  solution  on  other  lines ;  hence  the  author  feels  less  hesitancy 
in  questioning  the  premises  on  which  these  unsatisfactory  conclu- 
sions rest. 

Among  those. whose  works  are  utilized  with  gratefulness  the 
author  especially  acknowledges  his  indebtedness  to  Doctor  Charles 
Greely  Abbot  and  his  able  assistant,  Mr.  F.  E.  Fowle,  the  late  Pro- 
fessor Hilgard,  and  Professor  Chas.  Schuchert.  To  the  first  named 
for  their  notable  researches  in  solar  and  atmospheric  physics ;  to 
Professor  Hilgard  for  adverse  changed  into  favorable  criticism ; 
and,  to  Professor  Schuchert  for  his  valuable  epitome  of  the  facts  of 
paleontology  and  geology  bearing  upon  the  subject. 

The  author  feels  gratified  by  the  references  to  and  endorsements 
of  some  of  his  interpretations  by  Professor  F.  H.  Knowlton,  of  the 
U.  S.  Geological  Survey,  in  his  excellent  contribution  in  Vol.  30, 
of  the  Bulletin  of  the  Geological  Society  of  America. 

MARSDEN  MANSON. 

BERKELEY,  CALIF.,  Jan.  6,  1922. 


PREFACE 

The  object  of  this  work  is  to  offer  an  interpretation  of  the  causes, 
conditions  and  controlling  principles  of  the  climates  which  the  earth 
has  manifestly  undergone  during  Geologic  Ages  and  the  Modern 
Era.  The  most  important  of  these  relate  to  the  present  and  near 
future,  but  the  great  questions  involved  cannot  be  fully  considered 
and  set  forth  unless  the  whole  range  of  the  phenomena  of  climates 
and  of  the  energies  and  the  changing  conditions  under  which  they 
have  acted  be  taken  up  in  their  entirety  and  in  their  intricate  relations. 

Climatic  changes  do  not  strictly  belong  to  Geology  and  relate 
more  intimately  to  Meteorology  and  Atmospheric  Physics.  But 
these  changes  are  recorded  in  the  crust  of  the  earth,  which  so  entirely 
belongs  to  geology  that  most  of  the  special  studies  of  the  causes  of 
the  changes  of  climates  recorded  therein  have  been  made  by  Geol- 
ogists. The  Astronomer  and  Physicist  have  added  much  to  the 
knowledge  of  the  subject,  and  their  contributions  will  also  be  freely 
utilized  in  the  present  essay. 


AUTHORITIES  QUOTED  OR  REFERRED  TO 

PAGE 

Abbot  and  Fowle 1 1,  19,  20 

Arrhenius 32 

Barnard 12 

Barrell 21 

Bartholomew    1 1,  56,  58 

Branner  34 

Campbell    12 

Chamberlin 21 

Chamberlin  and  Salisbury 12,  23,  36,  55,  56,  59 

Coleman 27 

Croll 9,  30 

Davis,  W.  M 23 

Fowle,  see  Abbot  and  Fowle. 

Geikie,  Sir  A 31,  56,  59 

Geikie,    Jas 39,  51 

Harmer 44 

Hershel    12 

Hilgard  29,  34 

Joly 19 

Kelvin    19 

Knowlton  19,  21 

Knowlton,  White  and 37,  50 

Maury 30 

Reeds 10 

Reid    19 

Salisbury,  see  Chamberlin  and  Salisbury. 

Schuchert    1 1,  14,  26,  27,  47,  49,  50,  52,  55,  56,  59 

Scott 14 

Shackelton • 14 

Slipher,  E.  C 12 

Taylor    14 

White  and  Knowlton    37,  So 

Woeikof ..* 9 


CONTENTS  PAGE 

Preface    5 

Acknowledgments     4 

Authorities  Quoted  or  Referred  to 6 

PART  I 

The  Scope  of  the  Problems 9 

The  Basis  of  the  Present  Interpretation 10 

The  Leading  Authorities  Used  in  this  Essay 10 

Analogies  Presented  by  Other  Planets • 12 

Classification  and  Range  of  the  Phenomena  to  be  Explained 13 

The    Geologic   Record    of    Climates   and    Certain    Postulates    Established 

Thereby  14 

Analogies   and   Apparent   Anomalies  of   the   Two   Periods   of   Maxi- 
mum Glaciation 16 

Reasons    for    Doubting   the   Assumption    of    Solar    Control    of    Geologic 

Climates    18 

Reconsideration  of  the  Basis  of  Previous  Efforts  to  Solve  the  Problems 

of  Climates 18 

The  Inadequate  Basis  of  Mathematical  Calculations  of  the  Availability 

and  Duration  of  Earth  Heat  as  a  Climatic  Factor 18 

The  True  Radiating  Surface  of  the  Earth 20 

Heat  Conservation  Agencies 20 

The  Omitted  Factors   20 

Rejection  of  the  Assumption  of  Solar  Control  of  Geologic  Climates  and 
of  the  Results  of  Mathematical  Calculations  which  Are  used 

to  Fortify  this  Assumption 21 

The  Lessons  of  Pleistocene  Deglaciation 25 

The  Non- Availability  of  Both  Sources  of  Heat  During  Glaciations 27 

The  Influences  of  Solar  Radiation 30 

Effects   of   Gouds 30 

Ocean  Temperatures  and  Their  Effects 31 

The  Ocean  Temperatures  of  Pleistocene  Time 32 

The  Critical  Ocean  Temperatures  in  the  Maintenance  of  the  Cloud  Sphere 

in  Various  Zones 33 

Effects  of  Solar  Radiation  During  the  Prevalence  of  Warm  Oceans 34 

Control  of  Glaciations  and  Deglaciations — Effect  of   Clouds  During  the 

Prevalence  of  the  Two  Sources  of  Heat 36 

Conditions  of  Glaciation  39 

Summary  of  the  Causes  and  Conditions  of  Glaciations  and  Deglaciations, 

and  of  Interglacial  Epochs 41 

Classification    of    Glacial     Periods,    Deglaciations,     and     Interglacial 

Epochs    43 

The  Establishment  of  Solar  Climatic  Control 44 

The  Climatic  Transition  Era 46 


5  CONTENTS 

PART  II 

Application  of  the  Principles  Herein  Set  Forth  to  the  Facts  of  Paleontology 
and  Geology  as  Compiled  and  Discussed  by  Professor  Charles 

Schuchert  in  "  Climates  in  Geologic  Time  " 47 

Ocean  Temperatures  During  Geologic  Climates 49 

Comparison  of  the  Curves  of  Continental  and  of  Ocean  Temperatures. .  50 
The  Periods  of  Mountain  Making  or  of  "  Changes  in  the  Topographic 

Form  of  the  Earth's  Surface." 51 

A  Cooling  and  a  Warming  Earth 54 

A  Cooling  Earth   54 

A  Warming  Earth    55 

Permo-Carboniferous    and    Pleistocene    Glaciations    and    Interglacial 

Epochs    55 

Permo-Carbonif e/ous  Glaciation 55 

Climatic    Conditions    Between    Permo-Carboniferous    and    Pleis- 
tocene Time  57 

Pleistocene  Glaciation  58 

Interglacial  Epochs   59 

PART  III 

Recapitulation  of  Conclusions  and  Their  General  Application 61 

Summary  of  Conclusions 61 

Possibility  of  Future   Glaciations    63 

Application  of   Conclusions 64 


THE  EVOLUTION  OF  CLIMATES 
PART  I 

THE  SCOPE  OF  THE  PROBLEMS 

The  most  important  problem  in  terrestrial  physics  ....  and  the  one 
which  will  ultimately  prove  the  most  far  reaching  in  its  consequences,  is: 
What  are  the  physical  causes  which  led  to  the  Glacial  Epoch  and  to  all 
those  great  secular  changes  of  climate  which  are  known  to  have  taken 
place  during  Geological  Ages?  (Dr.  Croll,  "Climate  and  Cosmology.*') 

An  attentive  study  of  the  physical  Geography  of  the  earth  and  its 
influences  on  Climate,  together  with  a  judicious  application  of  the  simplest 
physical  theories,  will  enable  us  to  gain  by  and  by  a  better  knowledge  of 
Geological  Climates.  (Prof.  A.  Woeikof,  "Nature,"  March  2,  1882, 
p.  426.) 

The  principal  problems  are  covered  by  the  questions : 

What  were  the  causes  and  conditions  which  during  the  greater 
part  of  geologic  time  maintained  eras  of  tropical  and  warm  temperate 
climates  of  high  humidity  and  wide  distribution,  broken  by  frequent 
and  comparatively  short  glaciations  and  deglaciations  of  continental 
areas  in  low  and  middle  latitudes,  while  oceans  and  high  latitudes 
remained  warm? 

Why  should  two  of  these  be  zonal  glaciations  of  marked  severity, 
the  first  in  tropical  latitudes  while  oceans  and  polar  latitudes  still 
remained  mild  ;  the  second,  in  middle  and  polar  latitudes,  was  a  period 
of  "  Phenomenal  glaciation  "  which  followed  the  widespread  cold 
temperate  conditions  of  Pliocene  time  and  of  which  "  the  whole 
world  felt  its  effects  "  ? 

What  were  the  energies  and  conditions  which  caused  this  glaciation 
to  include  a  series  of  short  advances  and  retreats,  or  "  interglacial 
epochs,"  gradually  merging  into  the  existing  conditions  of  a  zonal 
arrangement  of  climates  different  from  any  other  which  ever 
prevailed  ? 

To  what  stage  are  these  new  conditions  tending? 

What  analogies  prevail  between  these  great  changes  and  possible 
conditions  upon  other  members  of  the  solar  system? 

These  changes  of  climates,  during  the  vast  eras  between  the 
earliest  Proterozoic  and  the  Modern  Era  offer,  therefore,  an  in- 
timately related  and  complicated  group  of  problems  that  has  not 
been  acceptably  solved. 


IO  THE   EVOLUTION    OF    CLIMATES 

These  failures  to  reach  a  satisfactory  solution  throw  suspicion 
upon  the  premises  upon  which  these  unsatisfactory  solutions  rest, 
which  suspicion,  to  the  seeker  for  truth,  not  only  warrants  but  re- 
quires their  rejection. 

There  are  two  premises,,  one  assumed  and  the  other  purporting 
to  rest  upon  mathematical  demonstrations,  which  the  studies  result- 
ing in  this  work  thus  mark  for  rejection ;  the  first  is  the  generally 
accepted  but  unproved  assumption,  that  solar  radiation  alone  con- 
trolled the  distributions  of  temperature  and  ice  antedating  the  Modern 
Era;  the  second  is,  that  mathematical  calculations  resting  upon  as- 
sumed premises  and  omitting  far  larger  and  more  important  factors, 
establish  that  the  extremely  low  conductivity  of  the  forming  crust 
and  the  small  amount  of  heat  held  within  a  shell  of  the  lithosphere 
of  an  assumed  thickness  and  temperature  justify  the  conclusion 
that  the  influences  and  control  of  earth  heat  were  of  short  duration, 
and  hence  the  only  other  source  of  heat,  solar  energy,  has  alone 
controlled  the  climates  of  geologic  time. 

These  two  premises  will,  therefore,  be  rigidly  questioned  as  to 
their  basis  and  fortification  by  mathematical  calculations  purporting 
to  buttress  them.  If  found  to  rest  upon  an  unproved  assumption 
or  inadequately  fortified  they  will  be  rejected. 

THE    BASIS    OF    THE    PRESENT    INTERPRETATION 

An  attempt  will  then  be  made  to  interpret  the  secular  changes  of 
climates  upon  the  basis  that  the  limited  and  fluctuating  supply  of 
earth  heat  and  its  cognate  energy  radio-activity  converted  into  heat, 
under  the  highly  conservative  conditions  imposed  by  water  in  its 
various  forms  and  the  utilization  of  solar  energy  as  a  conservative 
factor  throughout  geologic  time  were  competent  to  maintain  the 
narrow  limits  of  temperatures  known  to  have  prevailed;  and,  that 
under  these  conditions  the  limited  supply  of  earth  heat  was  recorded 
as  a  controlling  factor  in  all  geologic  time  until  the  inauguration  of 
the  sole  control  in  the  Modern  Era  of  the  greater  and  more  constant 
source — solar  energy.  In  other  words,  an  appeal  will  be  made  only 
to  the  factors  which  have  always  been  of  importance  in  determining 
climates.1 

THE  LEADING  AUTHORITIES  USED  IN  THIS  ESSAY 

In  addition  to  the  standard  texts  and  treatises  heretofore  utilized, 
the  author  finds  two  recent  works  well  fitted  for  the  presentation  of 

1  Dr.  Chester  A.  Reeds.    Science,  Jan.  7,  1921,  p.  22. 


MARSDEN    MANSON  II 

the  principles  and  facts  to  be  utilized  in  this  attempt  to  solve  the 
problems  herein  essayed. 

The  energies  and  conditions  which  control  climatic  variations  and 
the  general  physics  of  the  atmosphere  have  recently  been  more  firmly 
established  by  the  exhaustive  studies  and  extended  observations  by 
Dr.  Abbot  and  Mr.  Fowle.1  The  author,  therefore,  bases  this  effort 
to  interpret  the  variations  of  past  and  present  climates  and  to  deter- 
mine the  causes,  conditions  and  mode  of  action  of  the  energies  pro- 
ducing them  largely  upon  the  principles  which  the  results  of  the 
above  studies  and  observations  confirm ;  and  upon  the  principles  and 
facts  given  in  Bartholomew's  Physical  Atlas,  Vol.  Ill,  Meteorology. 

Another  of  the  Smithsonian  publications  will  be  fully  used ;  this 
work  is  entitled  "  Climates  in  Geologic  Time,"  f  by  Professor  Charles 
Schuchert,  of  Yale  University.  It  is  such  a  comprehensive  and 
authoritative  epitome  of  all  the  facts  of  paleontology  and  geology 
bearing  upon  the  subject  of  climatic  variations,  that  the  author 
accepts  it  as  a  succinct  statement  of  the  records  in  the  case.8 

It  is  not  often  that  a  student  of  a  difficult  and  controverted  problem 
finds  in  the  publications  of  an  Institution  of  high  standing  nearly  all 
the  principles  and  the  facts  which  are  needed  to  attempt  the  solution 
of  the  problem. 

The  first  of  these  publications  gives  the  results  of  the  elaborate 
researches  and  study  of  the  action  of  water  vapor  and  clouds  upon 
the  wave  lengths  of  the  entire  spectrum.  These  researches  fully 
confirm  principles  previously  applied  by  the  author  in  earlier  attempts 
to  solve  the  problems  of  climates.  The  second  is  an  authoritative 
compilation  of  the  facts  of  Geology  and  Paleontology  bearing  on  the 
subject. 

The  author  hopes  that  in  this  application  of  these  works — the 
one  for  the  principles  and  the  other  for  the  facts — he  may  aid,  in 
an  humble  way,  in  carrying  out  the  noble  motto — 

"For  the  Increase  and  Diffusion  of  Knowledge  among  Men." 

1  Annals  Astrophysical  Obs.,  Smithsonian  Institution,  Vols.  II-III. 

2  Report    Smithsonian   Institution,    1914,   pp.   277-311.     Also   The    Climatic 
Factor,  Dr.  Ellsworth  Huntington  Publication  No.  192  of  the  Carnegie  Insti- 
tution of  Washington. 

3  There  is  doubtless  a  very  marked  difference  in  the  interpretation  given  by 
the  author  to  the  facts  massed  in  the  masterly  work  of  Prof.  Schuchert.    For 
this  the  author  apologizes;  but  he  feels  the  more  indebted  by  reason  of  this 
difference  from  an  authority  not  sharing  this  interpretation. 


12  THE   EVOLUTION    OF    CLIMATES 

ANALOGIES    PRESENTED    BY    OTHER    PLANETS 

The  conclusions  herein  reached  are  so  general  that  they  have,  at 
least  an  inferential  bearing,  upon  the  conditions  apparently  reached 
upon  "  The  other  members  of  the  family  of  planets  to  which  the 
earth  belongs." 

More  than  one  and  one-third  centuries  ago  Sir  Wm.  Herschel 
gave  the  results  of  his  observations  and  studies  of  the  polar  snowcaps 
of  Mars  and  summarized  them  as  follows : 

The  analogy  between  Mars  and  the  earth  is,  perhaps,  by  far  the  greatest 
in  the  whole  solar  system.  Their  diurnal  motion  is  nearly  the  same,  the 
obliquity  of  their  respective  ecliptics,  on  which  the  seasons  depend,  is  not  very 
different;  of  all  the  superior  planets  the  distance  of  Mars  from  the  sun  is  by 
far  the  most  alike  to  that  of  the  earth,  nor  will  the  length  of  the  Martian  year 
appear  different  from  that  which  we  enjoy. 

If,  then,  we  find  the  globe  we  inhabit,  has  its  polar  regions  frozen  and 
covered  with  mountains  of  ice  and  snow,  that  only  partly  melt  when  exposed 
to  the  sun,  I  may  well  be  permitted  to  surmise  that  the  same  causes  may 
probably  have  the  same  effects  on  the  globe  of  Mars,  that  the  bright  polar 
spots  are  owing  to  the  vivid  reflection  from  frozen  regions,  and  that  the 
reduction  of  those  spots  is  to  be  ascribed  to  the  sun.1 

The  earth  is  in  no  very  special  way  distinguished  as  a  planetary  body.2 

In  reference  to  the  melting  of  the  south  polar  snows — I  speak  of  these  as 
"  snows  "  for  I  feel  perfectly  convinced  that  the  polar  caps  of  the  planet  Mars 
are  as  much  ice  and  snow  as  that  which  we  have  to  deal  with  terrestrially 
every  winter.8 

Some  of  the  planets  of  our  solar  system  may  be  passing  through  stages  of 
existence  that  the  earth  experienced  long  ago,  and  others  of  our  planets  may  be 
approximate  examples  of  what  is  in  store  for  the  earth.4 

Linked,  therefore  with  the  climatic  development  of  the  earth  are 
questions  touching  the  stages  reached  in  the  planets  which  are  appar- 
ently more  advanced  and  of  those  which  may  be  less  advanced  than 
the  earth;  for,  whatever  may  have  been  the  dates  and  modes  of 
their  origin,  differences  in  mass,  distance  and  environment  may  have 
varied  the  rate  of  development  of  each.  At  any  particular  period 
progress  cannot  have  been  the  same  for  all,  and  we  find  each  one 
in  that  particular  stage  which  the  conditions  just  named  have  per- 
mitted it  to  reach.  All  are  doubtless  governed  by  the  same  general 
laws,  and  must  be  progressing  toward  the  same  general  condition.6 

1  Phil.  Trans.  Vol.  LXXIV,  p.  260. 

2  Chamberlin  and  Salisbury,  Geology,  Vol.  II,  p.  2. 

3  Dr.  E.  E.  Barnard,  Popular  Astronomy,  1895. 

4  Dr.  W.  W.  Campbell,  Science,  N.  S.,  Vol.  LVI,  No.  1169,  p.  513,  May  25, 

1917. 

5  Manson  Astronomical  Soc.,  Pacific  Coast  Vol.  VII,  1895,  pp.  53-57. 

E.  C.  Slipher,  ib.  Vol.  XXXIII,  No.  193,  1921,  pp.  127-139,  and  especially 
PP-  9,  137-139. 


MARSDEN    MANSON  13 

The  conclusions  reached  in  this  work  will  therefore  be  tested  by 
the  analogies  expressed  by  the  above  quoted  authorities,  in  order 
to  secure  any  general  confirmation  which  they  may  add. 

CLASSIFICATION    AND   RANGE   OF   THE    PHENOMENA   TO    BE 

EXPLAINED 

The  phenomena  for  which  explanations  are  to  be  attempted  are 
so  correlated  that  a  satisfactory  assignment  of  the  controlling  causes 
and  conditions  must  embrace  them  all — no  one  phase  can  be  separated 
out  for  study  although  the  range  is  wide. 

(1)  In  time  they  embrace  the  entire  geologic  past,  the  present 
era  and  an  indication  as  to  the  trend  of  activities  yet  marking  the 
progressiveness  of  glacial  retreat.1 

(2)  In  range  they  embrace : 

(a)  The   present   concurrent  existence  of   zones   of   temperate, 
tropical  and  torrid  climates  in  middle  and  low  altitudes,  and  of 
glacial  climates  in  high  latitudes,  each  zone  of  which  is  inhabited 
by  groups  of  life  especially  adapted  to  its  climatic  conditions  and  is 
slowly  emerging  from  Pleistocene  glaciation,  the  greatest  recorded 
in  the  crust  of  the  earth  ; 

(b)  The   past    Permo-Carboniferous    distribution    of    glaciations 
the  reverse  in  latitudinal  distribution  of  those  during  the  Pleistocene 
namely,  the  glaciation  of  tropical  latitudes  concurrent  with  the  pre- 
valence of  genial  climates  in  high  latitudes ; 

(c)  The  short  period  deglaciations  and  reglaciations  during  each 
of  the  above  widely  separated  zonal  glaciations ;  the  last  merged  into 
present  conditions,  and  the  former  merged  into  a  world  wide  geniality 
more  tropical  than  the  polar  mildness  prevailing  during  the  maximum 
glaciation  of  tropical  latitudes  ; 

(d)  Ages  of  universally  temperate  and  tropical  climates  inter- 
spersed with  short  glacial  epochs  during  which  ice  covered  areas  in 
various  latitudes  and  gave  place  to  universal  geniality. 

(3)  They  call  for  an  explanation  of  the  phenomena  of  the  present 
era  with  extremes  of  heat  and  cold,  of  aridity  and  precipitation,  of 
frigidity  and  torridity  probably  exceeding  in  range  any  ever   re- 
corded ;  and,  how  these  developed  from  Geologic  Climates. 

(4)  Also  for  an  explanation  of  the  progressive  retreat  of  glacia- 
tion in  polar  latitudes  and  an  indication  of  the  probable  cumulative 
effects  of  the  energies  and  conditions  now  active  in  this  deglaciation. 

Attempts  to  explain  these  apparently  anomalous  groups  of  climatic 
phenomena  have  been  principally  directed  to  the  problems  of  glacia- 

1  Science,  N.  S.,  Vol.  XLVI,  pp.  639-640;  ib.,  Vol.  XLVII,  pp.  487,  488. 


14  THE   EVOLUTION    OF    CLIMATES 

tion  and  deglaciation,  although  these  do  not  form  an  integral  pro- 
blem, but  are  essential  parts  of  the  complicated  whole. 

These  complications  are  such  that  they  have  been  and  are  the 
most  controverted  fields  of  speculation  and  research  before  several 
generations  of  scientists.  The  writer,  however,  believes  that  the 
foundation  for  their  satisfactory  solution  will  be  laid  after  the  re- 
jection of  improperly  fortified  assumptions  and  upon  the  applica- 
tion of  the  present  knowledge  of  the  physics  of  the  atmosphere  and 
of  the  properties  of  water  in  its  various  forms  and  under  various 
conditions  in  their  action  upon  the  radiations  emitted  by  the  sun  and 
by  the  earth;  and,  that  corroborative  evidence  will  be  found  in  the 
conditions  existing  upon  some  of  the  other  planets. 

The  task  of  laying  this  foundation  will  be  undertaken  in  this  work. 
If  properly  laid  it  will  stand  of  itself  and  sustain  the  superstructure. 

THE  GEOLOGIC  RECORD  OF  CLIMATES  AND  CERTAIN  POSTU- 
LATES ESTABLISHED  THEREBY 

The  records  of  the  variations  of  the  climates  which  the  earth  has 
passed  through  and  the  stage  now  passing  before  us  are  generally 
acknowledg^ to  be  deeply  complicated;  and,  that  no  satisfactory 
explanation  of  either  the  major  or  minor  changes  has  been  made. 

The  complications  began  with  the  recognition  of  the  reality  of 
the  Ice  Age  or  Glacial  Period  of  Pleistocene  time,  during  which 
glaciations  reached  their  maxima  in  middle  or  temperate  latitudes 
and  extended  into  polar  latitudes,  and  the  oceans  became  glacial  in 
middle  and  high  latitudes. 

Still  more  intricate  complications  were  added  upon  the  segrega- 
tion of  at  least  four  interglacial  epochs,  or  short  warm  epochs, 
between  successive  retreats  and  advances  in  Pleistocene  glaciation.1 
These  epochs  were  first  recognized  in  middle  latitudes  where  this 
great  glaciation  fluctuated  and  finally  merged  into  the  zonally  dis- 
posed climates  of  today  and  has  retreated  to  polar  latitudes,  where 
this  retreat  is  yet  progressing  at  a  rate  which  calls  for  the  deglacia- 
tion  of  these  regions  within  a  period  which,  geologically  considered, 
is  not  remote. 

Complications  were  also  added  by  the  necessity  of  accounting  for 
other  glaciations  in  earlier  eras ;  of  these  one  of  the  most  extended 
and  remarkable  was  in  Permo-Carboniferous  time,  during  which  the 
glaciations  were  localized  in  two  wide  zones  between  15°  and  35° 
North  and  South  latitude.  During  this  glaciation  of  tropical  lati- 

1  Schuchert,  L.  c.,  p.  304. 


MARSDEN    MANSON  15 

tudes  a  broad  zone  in  equatorial  latitudes,  and  middle  and  high 
latitudes  escaped.  This  glaciation  was  followed  by  the  wide  spread 
geniality  of  Triassic  time. 

Not  only  are  these  minor  complications  or  interglacial  epochs 
presented  during  the  maximum  glaciations  of  middle  latitudes  and 
as  these  gave  way  to  the  zonal  ameliorations  yet  progressing,  but 
they  are  also  recognized  during  the  vast  Permo-Carboniferous  glacia- 
tions of  tropical  latitudes  which  gave  way  to  the  universally  mild 
climates  of  Triassic  time. 

We  therefore  confront  a  group  of  complications  in  regard  to  the 
distribution  of  temperatures  and  glacial  ice  involving  vast  eras  of 
uniformly  temperate  or  tropical  climates  interspersed  with  short 
glacial  periods  in  which  glaciation  was  nonconformable  to  both  pre- 
ceding and  succeeding  geniality  as  well  as  to  the  solar  controlled 
climates  of  today. 

These  great  changes  in  climates  date  back  into  the  earliest  geologic 
records,  extend  to  the  present,  and  reach  forward  into  an  immediate 
future  in  which  progressive  deglaciations  of  now  useless  polar  wastes 
marks  the  extension  of  productive  areas.1 

Scott :  "  All  these  evidences  and  many  others  which  space  will 
not  allow  me  to  mention  lead  up  to  one  great  fact — namely,  that  the 
glaciation  of  the  Antarctic  regions  is  receding." 3 

"  The  ice  is  everywhere  retreating." ' 

Shackelton :  "  Some  time  in  the  future  these  lands  will  be  of  use 
to  humanity."  4 

Taylor,  Geologist  of  Scott's  Expeditions,  speaks  with  confidence 
of  the  passage  of  the  Ice  Age  from  Antartica.5 

Standing  strongly  out  from  these  complications  are  some  broad 
and  significant  facts  which  throw  very  rigid  conditions  around  any 
assumptions  which  may  be  suggested  and  stubbornly  hold  their 
grounds  against  any  "  advances  of  discovery  "  which  may  happen 
to  be  in  the  wrong  direction. 

Among  these  facts  are  the  following : 

(i)  None  of  these  glaciations  were  conformable  to  present  dis- 
tribution of  temperatures  nor  occurred  in  latitudes  which  could  have 
been  exposed  to  solar  radiation  of  an  efficiency  equal  to  that  now 
deglaciating  polar  latitudes. 

1  Science,  N.  S.,  Vol.  XLVI,  pp.  639-640.    Dec.  29,  1917. 
*  National  Antarctic  Expedition  1900-1904,  Vol.  I,  p.  94. 
8  Scott's  Last  Expedition  Vol.  II.  pp.  294  and  286,  photograph   following 
p.  286  and  p.  292. 

4  Lecture  to  Commonwealth  Club,  San  Francisco,  Nov.  7,  1916. 

5  Scott's  Last  Expedition,  Vol.  II,  p.  288. 


1 6  THE   EVOLUTION    OF   CLIMATES 

(2)  All  glaciations  were  inaugurated  and  effected  during  periods 
in  which  the  temperatures  of  oceans  were  more  uniformly  distributed 
and  higher  than  those  which  have  prevailed  since  Pleistocene  glacia- 
tion  began  to  decline. 

(3)  Each  of  the  maximum  glaciations  was  zonally  disposed;  the 
earlier  in  tropical  latitudes,  now  the  zones  of  minimum  cloudiness 
and  precipitation  and  of  maximum  barometric  pressure  and  anticy- 
clonic  activity,,  it  was  preceded,  accompanied  and  succeeded  by  genial 
climates  in  other  latitudes  and  warm  oceans  in  all  latitudes.     The 
final  glaciation  was  localized  in  middle  latitudes  (although  extending 
into  polar),  now  the  zones  of  temperate  rains  and  of  denser  cloud- 
iness, of  secondary  minima  in  barometric  pressure  and  maximum 
cyclonic  activity;  it  was  preceded  by  cold  temperate  oceans,  accom- 
panied by  glacial  oceans  in  middle  and  polar  latitudes  and  succeeded 
by  oceans  which  are  of  so  low  a  temperature  in  the  aggregate  that 
inadequate  water  vapor  is  generated  to  sustain  glaciation  even  in 
polar  latitudes,  and  which  have  been,  as  well  as  continents,  dependent 
upon  solar  radiation  for  the  increase  in  temperature  which  has  fol- 
lowed the  last  glaciation. 

(4)  During  the  interglacial  epochs  deglaciations  were  conform- 
able,  and  glaciations   and   reglaciations   were   non-conformable  to 
climates  controlled  by  solar  radiation ;  or,  unless  we  assume  very 
short-period  and  wide  range  variations  in  solar  radiation,  not  war- 
ranted by  any  known  facts  nor  bases,  we  are  confronted  with  an 
alternation  of  exposures  to  solar  radiation  giving  deglaciations  with 
interceptions  of  this  exposure  giving  glaciations  and  reglaciations. 

ANALOGIES   AND  APPARENT  ANOMALIES  OF  THE   TWO   PERIODS   OF 
MAXIMUM    GLACIATION 

The  two  periods  of  maximum  glaciation,  the  Permo-Carboniferous 
and  Pleistocene,  present  remarkable  and  significant  analogies  and 
apparent  anomalies.  These  are  brought  out  by  contrasting  the  dis- 
tribution of  the  two  glaciations  in  latitude,  the  preceding  and  suc- 
ceeding distributions  of  climates,  and  the  fluctuating  deglaciations 
and  reglaciations  during  each. 

(1)  Permo-Carboniferous  glaciation  reached  its  maxima  in  the 
tropical  latitudes ;  Pleistocene  glaciation  reached  its  maxima  in  tem- 
perate and  polar  latitudes. 

(2)  Each  of  these  periods  of  maximum  glaciation  appears  to  have 
been  accompanied  by  a  series  of  short  interglacial  epochs. 

(3)  The  maximum  glaciation  of  tropical  latitudes  in  Permo-Car- 
boniferous time  was  preceded  by  the  non-zonal  tropical  climate  of 


MARSDEN    MANSON  17 

Carboniferous  time  and  merged  after  a  series  of  deglaciations  and 
reglaciations  or  interglacial  epochs,  into  the  non-zonal,  warm  tem- 
perate or  tropical  climate  of  Jurassic  time. 

The  maximum  glaciations  of  temperate  and  polar  latitudes  in 
Pleistocene  time  was  preceded  by  the  widely  distributed  and  cold 
temperate  climate  of  the  Pliocene,  and  merged  after  a  series  of 
deglaciations  and  reglaciations  or  interglacial  epochs,  into  the  dis- 
tinctly zonal  climates  of  the  Modern  Era  controlled  by  solar  radia- 
tion, under  which  deglaciation  is  yet  progressing  in  polar  latitudes. 

(4)  Both  of  these  great  zonal  glaciations  reached  maxima  in 
latitudes  which  could  not  have  been  glaciated  under  solar  control  of 
an  efficiency  equal  to  that  now  deglaciating  polar  latitudes. 

(5)  During  the  maxima  in  tropical  latitudes,  temperate  and  polar 
latitudes  escaped ;  and,  during  the  maxima  in  temperate  and  polar 
latitudes,  tropical  and  equatorial  latitudes  appear  to  have  had  the 
snow  line  lowered  several  thousand  feet. 

(6)  Deglaciations  in  each  case  appear  to  have  followed  lines  of 
zonal  exposure  to  solar  radiation. 

(7)  The  Permo-Carboniferous  glaciations  were  about  coincident 
with  the  limits  of  the  tropical  arid  belts,  and,  those  of  Pleistocene 
time  with  the  temperate  rain  belts  of  the  Modern  Era. 


1 8  THE   EVOLUTION    OF    CLIMATES 


REASONS  FOR  DOUBTING  THE  ASSUMPTION  OF  SOLAR  CON- 
TROL OF  GEOLOGIC  CLIMATES 

RECONSIDERATION  OF  THE  BASIS  OF  PREVIOUS  EFFORTS  TO  SOLVE  THE 
PROBLEMS  OF  CLIMATES 

The  assumption  of  solar  control  of  geologic  climates  is  a  premise 
in  all  efforts  to  solve  the  "  climate  controversy,"  and  all  conclusions 
resting  thereon  have  failed  in  the  crucial  test  of  fitting  the  geologic 
record  of  past  climates,  and,  require  "  other  factors  "  in  the  test  of 
meeting  the  requirements  of  the  short  "  interglacial  epochs  "  which 
characterized  the  Pleistocene  glaciation  of  temperate  and  Permo- 
Carboniferous  glaciation  of  tropical  latitudes. 

As  none  of  the  conclusions  heretofore  reached  has  been  found  to 
fit  the  geologic  record  of  climates,  it  has  been  impossible  to  accept 
them.  This  makes  it  manifest  that  some  assumption  or  premise  is 
radically  erroneous.  Prominent  among  these  premises  and  common 
to  nearly  all  attempts  to  solve  the  problems  of  the  evolution  of 
climates,  stands  this  unproved  and  badly  fortified  assumption  of 
solar  control  of  the  climates  of  all,  or  nearly  all,  of  geologic  time. 

THE    INADEQUATE    BASIS    OF    MATHEMATICAL    CALCULATIONS    OF    THE 

AVAILABILITY    AND   DURATION    OF   EARTH    HEAT   AS   A 

CLIMATIC    FACTOR 

The  problem  of  climatic  control  must  therefore  be  reconsidered, 
and  each  premise  or  assumption  which  has  entered  into  these  rejected 
and  unsatisfactory  conclusions  must  be  challenged,  irrespective  of 
the  universality  of  its  acceptance  and  however  firm  its  hold  upon  the 
scientific  mind;  for,  some  broad  and  important  premise  or  assump- 
tion must  be  radically  wrong  to  yield  results  which  fail  so  radically 
to  fit  the  geologic  record. 

There  can  be  little,  if  any,  doubt  that  at  some  period  within  the 
range  of  geologic  history  the  planetary  or  earth  heat,  however  de- 
rived, was  stored  in  its  primitive  oceans  and  of  influence  in  its 
climates;  and  that  denudations  and  ruptures  of  the  crust,  etc.,  set 
free  at  various  intervals  additional  increments  of  this  heat  which 
would  restore  in  whole  or  in  part  this  stored  heat  which  had  been  lost 
in  the  intervals. 

There  were  then  two  sources  of  potential  heat:  Earth  heat  and 
Solar  Radiation.  Each  had  its  functions,  and,  during  the  eras  of 
the  prevalence  of  both  sources  a  different  order  of  temperature  dis- 
tribution must  have  prevailed  than  prevails  since  the  lesser  source 


MARSDEN    MANSON  ig 

has  been  exhausted  and  only  the  more  powerful  source,  solar  radia- 
tion, remains. 

It  is  held  that  the  differences  in  these  two  climatic  eras  must  have 
been  so  marked  that  geologic  processes  and  the  differences  in  the 
distribution  of  temperature  as  recorded  by  life  and  ice  cannot  have 
failed  to  have  legibly  recorded  the  existence  of  the  dual  source,  the 
decadence  and  failure  of  the  lesser  and  the  establishment  of  the 
single  source  of  control  now  distinctly  prevailing.  It  is  not  permis- 
sible to  rule  out  the  influence  of  the  lesser  source  without  convincing 
geologic  evidence  of  its  decadence  and  failure  as  a  climatic  factor, 
and  of  the  distinct  establishment  of  the  greater. 

There  lies  directly  athwart  this  course  of  reconsideration  above 
laid  out,  the  almost  universal  acceptance  of  the  assumption  of  solar 
control  of  geologic  climates  fortified  as  it  is  by  the  results  of  mathe- 
matical calculations  of  the  limited  quantities  of  earth  heat  available 
in  an  assumed  depth  of  the  lithosphere  and  the  impossibility  of  its 
effects  through  conductivity.  The  results  show  possibilities  of  in- 
fluence of  such  slight  moment  that  they  are  insignificant  and  the 
available  supply  so  small  that  it  would  be  exhausted  so  as  to  be  in- 
considerable in  geologic  time.1 

But  these  calculations  are  based  upon  assumed  data  and  concep- 
tions which  in  the  light  of  the  principles  of  atmospheric  physics  and 
the  properties  of  water  in  its  various  forms,  particularly  as  estab- 
lished by  recent  researches  of  Abbot  and  Fowle,2  and  of  the  pos- 
sibilities of  the  store  of  energy  emanating  from  radio-active  sub- 
stances, appear  to  place  the  results  upon  an  inadequate  and  erroneous 
basis.3  For  instance,  it  is  found  therein  that  an  assumed  quantity  of 
heat  in  an  assumed  depth  of  the  cooling  and  forming  crust  was 
insufficient  to  produce  climatic  effects  of  any  duration  by  reason  of 
its  early  exhaustion  by  radiation ;  and,  that  this  source  could  not 
reach  the  surface  of  the  lithosphere  by  reason  of  the  extremely  low 
conductivity  of  the  crust. 

On  the  contrary  this  store  of  energy  having  been  locked  up  in  a 
crust  of  extremely  low  conductivity  and  slowly  liberated  therefrom 
by  other  processes  far  more  efficient  than  conductivity,  successively 

1Sir  William  Thomson  (Lord  Kelvin),  Mathematical  and  Physical  Papers, 
Vol.  Ill,  pp.  295-311  (Camb.  Ed.  1890).  Also  estimates  by  Prof.  Harry 
Fielding  Reid,  Science  Vol.  XXIX,  pp.  27-29,  Jan.  1909. 

2  Annals  Astrophysical  Observatory  Smithsonian  Institution,  Vols.  II,  and  III. 

8  See  Prof.  Joly's  Address  Geol.  Sec.  B.  A.  A.  S.  Dublin  Meeting,  1908. 
Report  Smithsonian  Institution,  1908,  pp.  355-384.  Also  Prof.  Knowlton's 
views,  Vol.  30,  Bull.  Geol.  Soc.  of  America. 


2O  THE    EVOLUTION    OF    CLIMATES 

stored  in  the  oceans,  and,  conserved  by  highly  efficient  agencies  were 
causes  of  the  long  duration  of  its  effects. 

Again  it  is  assumed  or  calculated  that  whatever  earth  heat  was 
brought  into -effect  during  geologic  eras  was  quickly  exhausted  by 
radiation.  On  the  contrary,  it  was  conserved  by  agencies  of  the 
highest  efficiency  and  stored  in  the  oceans  so  as  to  be  available  in 
prolonging  these  conserving  agencies. 

THE  TRUE   RADIATING  SURFACE  OF  THE  EARTH 

HEAT  CONSERVATION    AGENCIES 

The  surface  of  the  lithosphere  and  the  oceans  are  not  now  and 
never  could  have  been  exposed  to  loss  of  heat  by  radiation  into  space. 
"  The  true  radiating  surface  of  the  earth  as  a  planet  is  chiefly  the 
water  vapor  of  its  atmosphere  at  an  elevation  of  4000  meters  or 
more  above  sea  level."  : 

Moist  air  and  clouds  are  almost,  if  not  absolutely,  impenetrable 
to  the  long  wave  length  radiation  which  the  land  and  oceans  emit, 
and  clouds  intercept  solar  radiation  almost  completely,2  especially 
those  outside  the  visible  spectrum.  The  gauziest  cirri  intercept  all 
heat  radiations  in  the  solar  beam.3 

Beyond  this  "  true  radiating  surface  "  additional  conservative  ac- 
tivities are  and  must  always  have  been  active  up  to  and  in  the  region 
of  inverted  temperature  gradients.  Not  only  are  convection  currents 
turned  back  at  this  region,  but  from  above  this  region  more  solar 
derived  heat  may  have  been  radiated  for  one-half  the  time  than 
planetary  derived  heat  was  radiated  outward. 

Moreover,  upon  this  "true  radiating  surface"  and  the  clouds 
beneath  it  was  received  the  conservative  power  of  solar  radiation 
throughout  the  entire  period  of  the  earth's  existence.  The  ultimate 
loss  of  earth  heat  must  therefore  have  been  a  differential  process  of 
extreme  slowness. 

THE  OMITTED   FACTORS 

In  calculating  the  duration  of  earth  heat  as  a  climatic  factor  it  is 
important  to  consider  not  only  how  and  in  what  intervals  and  in- 
crements it  reached  the  surface  of  the  lithosphere  and  how  much 
was  available  within  an  assumed  thickness  thereof,  but  also  what 

1  Abbot  and  Fowle  Ann.  Astrophysical  Obs.  Smithsonian  Institution,  Vol.  II, 

P-  175- 

2  Geological    and    Solar    Climates,    Manson    1893,    p.    13    and    authorities 
there  cited. 

8  Ann.  Astrophysical  Obs.,  Smithsonian  Institution,  Vol.  II,  p.  134. 


MARSDEN    MANSON  21 

disposition  was  made  of  it  when  available  at  the  surface;  how  con- 
served; how  lost;  what  conservative  factors  and  energies  were 
active  in  prolonging  its  duration,  and  in  its  partial  replace- 
ment. 

Among  these  conservative  agencies  are : 

(1)  The  absorption  of  the  radiation  of  a  dark  body  by  water 
vapor  in  the  atmosphere. 

(2)  The  conservative  effects  of  clouds  on  (a)  the  escape  of  earth 
heat,  (b)  through  the  action  of  intercepted  solar  radiation. 

(3)  The  heat  stored  in  the  primitive  oceans  and  that  set  free  by 
crustal  ruptures,  denudation,  exposure  of  radio-active  substances, 
chemical  and  physical  actions  and  reactions,  etc. :  and  the  renewal  of 
conservative  factors  thereby. 

(4)  The  utilization  of  solar  radiation  during  the  prevalence  of 
effective  remnants  of  earth  heat  in  the  oceans. 

(5)  The  functions  of  each  of  the  two  sources  of  heat  and  their 
combined  effects  upon  the  duration  of  the  lesser  source. 

(6)  Were  the  values  of  each  of  these  factors  the  same  throughout 
geologic  and  present  time?    And  were  any  of  their  effects  modified 
during  the  prevalence  of  the  two  sources  ? 

Whilst  the  effects  of  these  factors  have  recorded  themselves  in 
geologic  history  and  their  relative  possibilities  can  be  judged,  it  is 
doubtful  whether  the  values  of  these  controlling  factors  are  known 
in  that  form  and  definiteness  which  mathematical  formulae  require. 
Their  omission  and  the  use  of  assumed,  inadequate  and  erroneous 
data  in  their  stead  is  fatal. 

The  fascinating  impressiveness  of  rigorous  mathematical  analysis  with  its 
atmosphere  of  precision  and  elegance,  should  not  blind  us  to  the  defects  of  the 
premises  that  condition  the  whole  process.  There  is  perhaps  no  beguilement 
more  insidious  and  dangerous  than  an  elaborate  and  elegant  mathematical 
process  built  upon  unfortified  premises.1 

The  exact  formulas  of  a  mathematical  science  often  conceal  the  uncertain 
foundations  of  assumptions  on  which  the  reasoning  rests  and  may  give  a  false 
appearance  of  precise  demonstration  to  highly  erroneous  results.2 

REJECTION  OF  THE  ASSUMPTION   OF  SOLAR  CONTROL  OF  GEOLOGIC   CLI- 
MATES  AND  OF  THE  RESULTS  OF   MATHEMATICAL   CALCULATIONS 
WHICH    ARE    USED    TO    FORTIFY    THIS    ASSUMPTION 

The  author  therefore  declines  to  be  beguiled  into  accepting  the 
results  of  the  calculations  above  referred  to,  which  omit  the  vital 


1  Prof.  Chamberlin,  Science,  Vol.  IX,  No.  235,  p.  889. 

2  Barrell,  Bull.  Geol.  Soc.  Am.  Vol.  28,  p.  749.     Knowlton,  Bull.  Geol.  Soc. 
Am.,  Vol.  30,  p.  565. 


22  THE   EVOLUTION    OF   CLIMATES 

and  important  factors  herein  pointed  out,  and  are  based  on  unforti- 
fied premises.  He  feels  obliged  to  reject  the  conclusions  as  "  in- 
competent, irrelevant  and  immaterial." 

It  is  held  that  both  earth  heat  and  solar  radiation  prevailed  as 
active  factors  in  temperature  control  during  all  of  the  eras  of  geologic 
history  and  until  the  Modern  Era  of  Solar  control ;  that  the  former 
was  available  as  ocean  stored  heat,  but  the  supply  was  held  in  the 
forming  crust  by  reason  of  its  low  conductivity  and  was  slowly 
made  available  by  denudation  and  the  exposures  of  radio-active 
materials,  etc.,  or  by  "  periodic  changes  in  the  topographic  form  of 
the  earth's  surface  "  which  made  increments  of  the  interior  sources 
of  energy  available.  These  increments  partially  restored  the  temper- 
ature inside  the  cloud  sphere  and  added  to  the  amount  of  heat  stored 
in  the  oceans  and  thus  replaced  in  part  that  slowly  lost  in  the  long 
intervals  between  the  successive  adjustments  and  ruptures  of  the 
crust  which  demark  the  time  divisions  of  geologic  history. 

The  conductivity  of  the  crust  of  the  earth  is  so  low  that  the  heat 
which  could  be  made  available  as  a  climatic  factor  through  this 
process  is  negligible,  except  for  very  short  periods  over  very  limited 
areas.  This  extremely  low  conductivity  was  therefore  one  of  the 
highly  conservative  factors  imposing  the  long  duration  of  this  source, 
and  its  liberation  is  recorded  in  the  denudation  of  the  crust,  the 
altered  and  unaltered  sedimentaries,  and  severe  crustal  ruptures  up 
to  the  Modern  Era. 

It  must  be  again  noted  that'  these  additions  to  ocean  stored  heat 
and  the  high  specific  heat  of  water  caused  the  oceans  to  fluctuate 
through  more  moderate  limits  than  continents,  and,  with  slight  fluc- 
tuations, to  retain  some  of  this  intermittently  liberated  heat  until 
the  close  of  Pleistocene  time,  when  for  the  first  time  boreal  ocean 
life  and  ice  cold  oceans  recorded  the  final  loss  of  earth  heat  by  that 
agent  most  competent  to  hold  it.  Moreover,  cold  oceans  do  not 
supply  the  water  vapor  necessary  for  severe  glaciations  nor  to  main- 
tain the  integrity  of  the  cloud  sphere  in  a'ny  latitude,  as  made 
manifest  by  present  cloud  density  and  by  the  deglaciations  which  have 
progressed  since  oceans  fell  to  the  temperatures  which  inaugurated 
the  Modern  Era. 

Now  oceans  "  the  world  over  tropical  or  sub-tropical  "  as  in  Lower 
Cambric  time;  "  world  wide  warm  water  conditions  "  of  Carbonifer- 
ous time ;  "  warm  throughout  the  greater  part  of  the  world  "  as  in 
Jurassic  time ;  or  when  "  polar  waters  were  cool  "  as  in  late  Pliocene 
time,  would  undoubtedly  generate  more  water  vapor  and  impose  a 
greater  cloud  density  and  persistency  than  now  prevails  with  polar 


MARSDEN    MANSON  23 

oceans  and  with  ocean  depths  ice  cold,  and,  only  the  surfaces  of 
oceans  in  equatorial,  tropical  and  temperate  latitudes  above  this 
degree.  Moreover,  oceans  are  now  dependent  upon  exposure  to 
solar  radiation  for  any  increase  in  temperature. 

Now,  with  warmer  and  still  cooling  oceans,  no  colder  in  their 
deeps  than  the  coldest  surface  temperatures,1  the  existence  of  a  cloud 
sphere  of  greater  extent  and  persistence  than  the  prevailing  52  per 
cent  of  permanent  cloudiness  over  the  earth's  surface  is  not  only  a 
legitimate  inference,  but  its  effects  are  geologically  recorded  in 
frequent  glaciations  of  latitudes  which  could  not  have  been  glaciated 
under  solar  control,  unless  it  be  assumed  that  the  intensity  of  this 
energy  was  greatly  reduced  or  that  its  effects  were  intercepted  by 
some  highly  efficient  agent.  Now,  neither  the  short  period  glacia- 
tions nor  the  still  shorter  interglacial  epochs  can  be  ascribed  to  solar 
control  or  to  variations  in  its  intensity,  for  these  variations  in  climate 
occurred  with  warm  oceans  and  in  all  glaciations,  except  the  last  of 
universally  colder  climates,  polar  latitudes  were  mild.  Mild  polar 
climates  and  warm  oceans  concurrent  with  glaciations  of  tropical 
latitudes  are  not  manifestations  of  the  solar  control  of  climates,  and 
no  effort  of  the  scientific  imagination  to  make  them  appear  as  such 
has  met  with  the  approval  of  the  scientific  judgment  and  the  con- 
tradictions and  anomalies  involved  in  trying  to  fit  these  facts  to  solar 
control  are  positive  and  insurmountable. 

In  Professor  Davis's  very  able  discussion  of  the  possible  causes 
and  conditions  of  the  glaciation  of  tropical  latitudes  in  Permian  time 
and  under  the  assumption  of  solar  control,  he  rejects  all  of  the 
causes  which  he  considers,  and  thus  negatives  solar  control  during 
this  glaciation  under  the  hypotheses  discussed.2 

It  is  therefore  held : 

(i)  That  earth  heat  stored  in  the  oceans  and  conserved  by  moist 
air  and  clouds  and  in  part  restored  in  and  above  "  the  true  radiating 
surface  "  by  the  effects  of  intercepted  solar  radiation,  imposed  its 
influences  until  its  exhaustion  was  registered  by  the  cold  oceans  of 
Pleistocene  time ;  that  during  all  of  geologic  time  the  two  sources 
were  active  in  determining  the  climates  of  the  earth;  the  lesser 
source  was,  under  the  conditions,  the  dominating  factor  and  was 
conserved  and  reinforced  by  the  greater  through  its  absorption  in  the 
upper  atmosphere ;  and,  by  its  admission  to  the  surface  by  temporary 
impairments  of  the  cloud  sphere. 

1  Chamberlin  and  Salisbury,  Geology,  Vol.  II,  p.  658. 
3  Bull.  Geol.  Soc.  Am.,  Vol.  17,  pp.  415-420. 


24  THE   EVOLUTION    OF    CLIMATES 

(2)  That  the  more  powerful  source,  solar  energy,  acted  as  a  con- 
servator until  it  was  intermittently  and  gradually  admitted  to  the 
lower  regions  of  the  atmosphere  and  to  the  surface  of  the  earth 
through  impairments  in  the  cloud  sphere;  these  impairments  first 
became  permanent  in  the  regions  of  least,  and  later  in  regions  of 
greatest  cloud  density  and  were  due  to  the  decreasing  amounts  of 
water  vapor  supplied  from  the  gradually  cooling  oceans ; 

(3)  That  this  admission  of  solar  energy  was  registered,  first  in 
the  partial  and  then  in  the  permanent  deglaciations  in  the  latitudes 
of  least  cloud  density  in  Permo-Carboniferous  time;  next  in  the 
partial,  fluctuating  and  permanent  deglaciations  in  the  latitudes  of 
greater  cloudiness  under  the  temperate  rain  belts  during  Pleistocene 
glaciation ;  and  finally,  as  recorded  by  the  progressive  deglaciation  of 
polar  latitudes; 

(4)  That  between  Triassic  and  Pleistocene  time,  both  inclusive, 
the  two  sources  prevailed  coincidently ;  earth  heat  control  prevailed 
in  regions   of  greatest  cloud   density,  and,   solar   radiation  in  the 
tropical  regions  of  least  cloud  density  which  condition  was  estab- 
lished at  the  close  of  Permo-Carboniferous  glaciation;  and  which 
was  extended  to  the  rest  of  the  world  at  the  dawn  of  the  Modern 
Era. 

(5)  That  between  Triassic  and  Pleistocene  time,  both  inclusive, 
a  variable  control  by  earth  heat  was  registered  in  the  glaciations 
recorded  at  the  close  of  Triassic  and  Cretacic  time  and  in  those  of 
Pleistocene  time,  which  latter  were  complicated  with  the  "  inter- 
glacial  epochs,"  and  finally  gave  way  to  the  Modern  Era, 

(6)  Finally  that  in  the  close  of  Pleistocene  glaciation  and  the 
complete  and  world  wide  establishment  of  solar  climatic  control  is 
recorded  the  most  profound  change  in  the  history  of  the  earth. 

It  therefore  cannot  be  assumed  that  variation  of  geologic  climates 
have  been  controlled  by  solar  variations,  for  the  distributions  neither 
of  temperature  nor  of  ice  has  been  conformable  thereto. 

With  warm  oceans  and  the  earth  swathed  in  clouds  maintained  by 
water  vapor  generated  by  its  own  heat,  it  would  make  no  difference 
in  its  surface  temperatures  to  double  or  halve  the  intensity  of  solar 
radiation.  The  time  of  earth  heat  exhaustion  would  be  increased  in 
one  and  reduced  in  the  other.  Mantled  in  clouds  formed  and  main- 
tained from  water  vapor  generated  by  its  own  heat  the  earth  could 
be  moved  up  into  the  orbit  of  Venus  or  out  into  that  of  Mars  with  no 
other  effect  upon  its  surface  temperatures  than  to  prolong  or  to 
shorten  the  period  of  control  of  its  own  heat  supply,  with  corres- 


MARSDEN    MANSON  2S 

J 

ponding  effects  in  the  establishment  of  solar  climatic  control,  and 
with  corresponding  expansions  or  contractions  ^>f  the  cloud  sphere. 

We  consequently  have  the  combined  effects  of  earth  heat  and  solar 
energy  to  deal  with  under  the  conditions  imposed  by  slowly  cooling 
oceans  and  a  forming  crust  gradually  losing  its  heat  to  water  by 
denudations,  etc.,  and  by  periodic  adjustments  of  its  form. 

It  must  be  noted  also  that  these  glaciations  and  deglaciations  im- 
posed irregular  variations  in  isostasy  by  withdrawing  uniformly  dis- 
tributed loads  from  ocean  bottoms  and  imposing  them,  to  a  greater 
degree  per  unit  of  area  and  non-uniformly,  as  ice  upon  continents : 
these  loads  having  been  distributed  at  times  upon  large  continental 
areas  irrespective  of  latitude;  in  Permo-Carboniferous  time  they 
were  distributed  in  the  broad  zones  between  15°  and  35°  North  and 
South  latitude ;  and,  in  Pleistocene  time  in  middle  latitudes,  notably 
on  the  great  continental  areas  in  the  Northern  Hemisphere.  After 
each  continental  overload  they  were  withdrawn  and  restored  to  the 
oceans  and  during  each  of  the  two  greater  glaciations  were  partially 
withdrawn  and  replaced  several  times. 

The  adjustments  and  readjustments  of  the  crust  due  to  these  dis- 
turbances of  isostasy  are  in  part  known  by  the  continental  record 
but  can  only  be  inferred  over  the  greater  portion  of  the  crust  covered 
by  the  oceans. 

THE  LESSONS  OF  PLEISTOCENE  DEGLACIATION 

The  progressive  deglaciation  which  has  proceeded  since  the  culmi- 
nation of  the  Ice  Age  has  imposed  very  rigid  conditions  upon  as- 
sumptions of  the  sources  of  temperature  control  by  recording  this 
control  in  legible  and  impressive  terms. 

The  records  in  the  temperate  latitudes  of  both  America  and 
Europe  are  particularly  significant:  (i)  These  latitudes  could  not 
have  been  glaciated  during  solar  control  of  an  effectiveness  now 
deglaciating  polar  areas.  Solar  energy  must  therefore  have  been 
intercepted  by  the  only  efficient  agent — namely,  the  constant  presence 
of  a  cloud  sphere  in  these  latitudes;  they  could  easily  have  been 
deglaciated  by  the  further  chilling  of  the  oceans,  which  would  im- 
pair the  efficiency  of  the  heat-intercepting  cloud  sphere,  which  in 
turn  would  expose  these  latitudes  to  the  direct  effects  of  that 
energy  which  is  proving  its  deglaciating  efficiency  even  in  polar  lati- 
tudes. A  slight  increase  in  ocean  temperatures  from  crustal  adjust- 
ments and  ruptures  would  slightly  rewarm  the  surface  of  the  ocean 
and  restore  the  intercepting  cloud  sphere  and  also  yield  the  water 


26  THE   EVOLUTION    OF    CLIMATES 

vapor  necessary  for  reglaciation  ;  upon  the  exhaustion  of  that  portion 
of  this  increment  which  reached  the  oceans  solar  energy  would  again 
deglaciate. 

These  alternations  of  control  manifestly  imposed  conditions  first 
favorable  to  glaciation  and  then  favorable  to  deglaciation ;  and  were 
imposed  some  four  or  more  times  in  both  North  America  and  in  cor- 
responding latitudes  in  Europe.  These  alternations  were,  therefore, 
not  due  to  short  period  fluctuations  in  the  intensity  of  solar  radiation, 
but  to  fluctuations  in  the  available  but  fading  earth  heat  as  set  free 
by  crustal  adjustments  etc.  The  effects  of  the  alternation  of  the  two 
sources  of  control  cannot  reasonably  be  ascribed  to  variations  in 
the  great  and  practically  constant  source — the  "  factors  other  than 
those  mentioned  "  by  Professor  Schuchert *  appear  to  be  supplied  by 
the  effects  of  increments  of  earth  heat  set  free  by  crustal  readjust- 
ments as  the  oceans  reached  the  critical  temperature  between  genera- 
ting a  sufficiency  or  an  insufficiency  of  water  vapor  to  maintain  the 
cloud  sphere — first  in  the  regions  of  least  cloudiness,  and  lastly,  in 
those  of  more  persistent  cloudiness — the  temperate  rain  and  cloud 
belts. 

The  interglacial  epochs,  of  the  Pleistocene  period,  occurred  before 
the  final  chill  of  the  last  glaciation  had  culminated  in  the  colder 
winters  of  the  Modern  Era,  and  hence  solar  energy  did  not  have  the 
chill  of  winter  to  remove  from  temperate  land  areas  before  the 
warmth  of  spring  could  be  established.  The  same  latitudes  were 
therefore  slightly  warmer  in  the  interglacial  epochs  than  at  present. 

1  L.  c.  p.  311.    Carnegie  Institution,  Pub.  192,  p.  298. 


MARSDEN    MANSON  2? 


THE  NON-AVAILABILITY  OF  BOTH  SOURCES  OF  HEAT  DURING 

GLACIATIONS 

As  the  weight  of  opinion  against  the  prevalence  of  the  effects  of 
earth  heat  up  to  the  Modern  Era  is  decidedly  preponderant,  and  as 
the  two  great  Institutions  of  research,  hereinbefore  referred  to,  have 
given  wide  publication  and  high  standing  to  this  opinion,  it  becomes 
necessary,  before  proceeding  farther,  for  the  author  to  state  specifi- 
cally his  reasons  for  dissenting  therefrom. 

In  order  to  disprove  any  possible  effect  of  earth  heat  as  a  climatic 
factor  Professor  Schuchert  cites  the  early  Huronian  glaciation  in 
Canada  as  proof  that  earth  heat  was  not  sufficient  to  prevent  such 
glaciation  even  in  this  remote  period  of  geologic  history.  ;<  The 
evidence  of  the  tillites  is  in  favor  of  the  view  that  the  glaciation  in 
Huronian  Canada,  was  not  '  the  work  of  merely  local  mountain 
glaciers  '  but  rather  due  to  '  the  presence  of  ice  sheets  comparable 
to  those  which  formed  the  Dwyka.'  *  *  *  "  "  This  implies  that  the 
climates  of  the  earlier  parts  of  the  world's  history  were  no  warmer 
than  those  of  later  times,  and  that  in  Lower  Huronian  times,  the 
earth's  interior  heat  was  not  sufficient  to  prevent  the  formation  of 
a  great  ice  sheet  in  latitude  46°." '  This  is  a  sound  implication,  so 
far  as  it  goes.  Carrying  it  to  its  logical  conclusion  it  applies  with 
equal  force  to  any  other  source  of  heat  which  may  be  assumed  to 
have  controlled  climates  during  that  period.  The  author,  although 
realizing  that  his  views  and  those  of  Professor  Schuchert  are  widely 
apart,  would  change  but  one  word  of  the  above  quotation,  namely, 
available  instead  of  "  sufficient." 

This  evidence  of  glaciation  shows  that  in  Lower  Huronian  times 
neither  of  the  sources  of  heat  was  available,  under  the  prevailing 
conditions,  to  prevent  the  glaciation  of  large  areas  in  the  interior  of 
continents,  in  this  case  only  one  degree  north  of  the  median  latitude 
between  the  equator  and  the  north  pole.  The  same  is  true  of  the 
maximum  glaciation  of  the  same  latitude  in  Pleistocene  time ;  or,  in 
the  period  of  maximum  glaciation  of  tropical  latitudes  in  Permo- 
Carboniferous  time,  when  earth  heat  was  not  available  to  prevent  the 
severe  glaciation  of  immense  continental  areas  in  tropical  latitudes ; 
neither  does  it  appear  that  solar  radiation  was  available  to  prevent 
these  glaciations,  even  in  the  zones  of  its  vertical  and  maximum 
effects. 

1  Smithsonian  Report,  1914,  p.  287.  Carnegie  Institution  Publication,  No.  192, 
p.  243.  Also,  Coleman,  Am.  Jour.  Science,  Vol.  23,  p.  192. 


28  THE    EVOLUTION    OF    CLIMATES 

If  these  glaciations  are  to  be  assigned  to  solar  control  it  must  be 
admitted,  either: 

That  solar  radiation  in  north  latitude  46°  in  two  cases,  and,  in 
the  zones  of  its  vertical  incidence  in  the  other,  fell  to  an  efficiency 
less  than  that  now  deglaciating  polar  latitudes ; 

Or  the  alternative,  that  it  was  intercepted  by  some  efficient  agent 
for  considerable  periods  of  geologic  time  when  earth  heat  was  not 
available  to  prevent  such  glaciations. 

There  is  no  warrant  for  assuming  that  solar  efficiency  should  have 
been  reduced  to  such  an  extremely  low  ebb — particularly  during  eras 
when  the  oceans  were  warm  and  capable  of  generating  sufficient 
water  vapor  to  yield  a  cloudiness  capable  of  effectually  intercepting 
it,  and.  the  concurrent  presence  of  mild  climates  in  polar  regions 
precludes  ascribing  Permo-Carboniferous  climates  to  solar  control. 

In  fact,  glaciations  only  appeared  when  neither  source  was  avail- 
able to  prevent  them,  the  lesser  and  fluctuating  source  having  been 
locked  up  in  a  non-conducting  crust  and  the  intervals  between  its 
liberation  having  been  long  enough  for  the  quickly  cooling  continents 
to  lose  their  heat  before  the  stored  heat  of  the  oceans  was  exhausted, 
which  stored  heat,  until  its  later  exhaustion,  maintained  a  dense 
cloud  formation.  The  more  powerful  and  constant  source  wa"s  not 
available  by  reason  of  being  intercepted  by  the  cloud  sphere  main- 
tained by  this  stored  heat  of  the  oceans.  This  interception  and  the 
utilization  of  this  great  source  as  a  conservator  of  the  conditions 
prevailing  on  the  earth's  surface  was  an  effective  agency  in  maintain- 
ing the  control  of  surface  temperatures  by  the  lesser  source  which 
fluctuated  in  its  availability  and  exhaustion,  and  which  failed  first 
to  maintain  land  areas  and  later  ocean  areas  at  mild  temperatures. 

Either  source  was  sufficient  to  remove  glaciation  when  conditions 
rendered  it  available,  as  evidenced  by  the  deglaciating  effects  of 
crustal  ruptures  in  the  earlier  Eras ;  and,  by  the  polar  deglaciations 
yet  progressing  from  the  direct  exposure  to  solar  radiation  which 
followed  the  chilling  of  the  oceans  to  about  the  point  of  maximum 
density  and  the  consequent  impairments  in  all  latitudes  of  the  cloud 
sphere  to  an  aggregate  extent  of  48  per  cent  of  the  earth's  surface. 

It  must  also  be  kept  in  mind  that  the  distributions  of  temperatures 
prior  to  the  Modern  Era,  were  not  conformable  to  those  imposed  by 
solar  control,  and  that  the  oceans  were  not  glacial  prior  to  Pleistocene 
time. 

It  appears  that  there  were  frequent  short  periods  during  which 
sufficient  heat  of  neither  source  was  available  to  maintain  tempera- 


MARSDEN    MANSON  2Q 

tures  above  glacial  conditions  upon  easily  chilled  continents ;  and, 
that  during  these  periods  earth  heat,  stored  in  the  oceans,  furnished 
abundant  water  vapor  to  be  condensed  into  glaciers  of  great  area  and 
depth,  and,  to  maintain  an  intercepting  cloud  sphere  of  such  efficiency 
that  temperate  and  tropical  latitudes,  which  could  not  have  been 
glaciated  under  solar  control,  were  deeply  and  widely  glaciated,  also 
that  upon  the  occurrence  of  maximum  glaciation  and  the  loss  of  the 
last  effective  increment  of  earth  heat  by  the  oceans,  they  ceased  to 
yield  sufficient  water  vapor  either  to  glaciate  or  to  shield  the  earth's 
surface  from  permanent  deglaciation  under  solar  radiation. 

During  all  of  these  glaciations  and  deglaciations  the  other  effects 
of  solar  radiation,  namely,  the  fixing  of  zones  of  maximum  and 
minimum  atmospheric  pressure,  of  consequent  minimum  and  max- 
imum cloudiness  and  precipitation  and  of  the  activities  of  anti- 
cyclonic  circulation,  were  not  interfered  with.  The  effects  of  these 
factors  of  climate  were  fixed  by  the  greater  and  more  constant  source 
of  heat  and  were  consequently  zonally  disposed  about  the  earth.1 

Either  source  was  therefore  sufficient  at  any  time  to  prevent 
glaciation  or  to  deglaciate ;  but  solar  energy  was  not  fully  available 
at  the  earth's  surface  until  the  close  of  Pleistocene  time,  although 
it  was  available  in  the  tropical  latitudes  of  least  cloudiness  subsequent 
to  the  final  deglaciation  of  these  latitudes  at  the  close  of  Permo- 
Carboniferous  glaciation.  After  this  deglaciation  a  dual  control 
appears  to  have  been  maintained,  Solar  control  in  tropical  latitudes, 
and  a  fading,  fluctuating  control  by  earth  heat  in  other  latitudes, 
until  its  final  exhaustion  in  later  Pleistocene  time. 

Earth  heat  was  not  available  to  prevent  glaciation  when  the  inter- 
vals between  its  liberation  from  the  crust  were  too  long,  but  as 
stored  heat  in  the  mtfre  slowly  cooling  oceans  it  was  available  to 
maintain  water  vapor  for  a  denser  cloudiness  than  now  prevails. 
For  the  foregoing  reasons,  and  others  more  specifically  given  later, 
it  is  held  that  earth  heat  was  an  effective  climatic  factor  during  all  of 
geologic  time,  that  its  effects  varied  in  intensity,  notably  upon  con- 
tinents; and,  that  glaciation  was  caused  by  the  interception  of  solar 
radiation  by  clouds  maintained  by  successive  increments  of  ocean- 
stored  earth  heat  during  intervals  between  its  liberation  from  the 
non-conducting  crust  long  enough  to  permit  land  areas  to  cool  below 
freezing ;  and,  that  no  glaciation  under  Solar  control  of  cli- 
mates has  been  recorded. 

1  Hilgard.  Proc.  International  Geol.  Congress,  Mexico,  1906. 


30  THE  EVOLUTION    OF   CLIMATES 

THE   INFLUENCES   OF   SOLAR    RADIATION 

The  influences  of  solar  radiation  have  been  undoubtedly  imposed 
upon  the  earth  throughout  its  existence.  Variations  in  the  conditions 
under  which  these  influences  have  been  imposed  have  within  them- 
selves the  potentials  of  profound  effects  upon  the  results.  This  is 
of  particular  moment  in  that  all  of  the  solar  effects  are  not  influenced 
to  the  same  degree  by  varying  conditions. 

It  is  therefore  necessary  to  briefly  review  the  influences  of  solar 
radiation  and  the  varying  conditions  under  which  they  have  been 
imposed.  This  also  is  the  more  necessary  when  it  is  considered  that 
some  of  the  forms  of  water  impose  different  conditions  upon  solar 
radiation  than  upon  radiation  from  the  earth.  Moreover,  solar 
radiation  in  fixing  the  zones  of  its  influence  restricts  certain  factors 
of  climate  in  some  zones  and  imposes  an  excess  upon  others. 

The  effects  of  none  of  these  factors  could  have  been  interfered 
with  during  geologic  time  except  those  of  heat,  which  is  intercepted 
by  clouds.  Therefore,  should  the  degree  or  loci  of  cloudiness  have 
varied,  marked  variations  in  heat  control  and  effects  must  have  fol- 
lowed and  must  have  been  recorded ;  variations  in  the  combined  in- 
fluences which  barometric  pressures  and  winds  could  have  imposed 
upon  clouds,  precipitation,  and  temperatures  must  also  have  occurred. 

Should  any  of  these  conditions  and  their  effects  be  omitted  in  the 
consideration  of  the  problems  of  climate  the  interpretation  of  the 
records  of  geologic  climates  and  of  their  transition  into  present 
climates  is  rendered  difficult  if  not  impossible. 

• 

EFFECTS  OF   CLOUDS 

The  intercepting  power  of  clouds  upon  the  radiations  emitted  from 
each  of  the  two  sources  of  heat  is  so  great  that  in  the  presence  of  an 
extensive  clouded  area  their  effects  are  kept  separate  and  apart.  The 
radiations  from  the  superior  source,  the  sun,  are  intercepted  to  such 
an  extent  that  the  wave  lengths  in  the  visible  spectrum  which  filter 
through  are  of  almost  negligible  effect  at  freezing  temperature  *  and 
those  of  the  infra  red  region  of  the  spectrum  are  almost,  if  not  en- 
tirely absorbed.  All  wave  lengths  emitted  by  the  inferior  source — the 
earth — are  almost  completely  absorbed  by  water  vapor  and  are  inter- 
cepted entirely  by  clouds.  Any  variations  in  the  degree  of  cloudiness 
would  therefore  impose  restrictive  variations  in  the  effects  of  both 
sources  of  heat,  shutting  out  solar  energy,  except  a  small  portion  of 

1  Maury,  Physical  Geography  of  the  Sea,  6  Ed.  p.  212  et  seq.  Croll,  Qimate 
and  Time,  p.  60,  Climate  and  Cosmology,  p.  51. 


f 


MARSDEN    MANSON  3! 


the  radiations  in  the  visible  spectrum  and  shutting  in  whatever  radia- 
tions the  earth  emitted.  If  the  temperature  of  the  oceans  were  such  as 
to  increase  the  amount  of  water  vapor  until  cloudiness  was  for  long 
periods  continuous,  the  controling  effects  of  the  two  sources  of  heat 
would  be  separate — those  of  the  superior  source,  solar  energy,  would 
be  principally  restricted  to  the  outer  surface  of  the  clouds,  and  the 
air  above  it  and  would  be  conservative ;  those  of  the  interior  source 
would  be  dominant  in  surface  temperatures  and  held  beneath  the 
cloud  surface,  subject  to  such  variations  as  the  available  increments 
of  this  source  would  impose  and  subject  farther  to  the  conditions 
imposed  by  atmospheric  circulation,  zones  of  cloudiness  and  precipi- 
tation and  barometric  pressures  as  fixed  by  solar  energy. 

OCEAN    TEMPERATURES   AND   THEIR   EFFECTS 

The  geologic  record  is  to  the  effect  that  at  no  time  prior  to  the 
Pleistocene  period  were  the  oceans  as  cold  as  at  present;  and,  the 
data  brought  together  by  Professor  Schuchert  indicate  that  they  were 
at  all  times  between  temperate  and  tropical  until  the  cold  temperate 
of  Pliocene  and  early  Pleistocene  time,  followed  by  the  glacial  tem- 
peratures of  late  Pleistocene  and  the  Modern  Era. 

Until  glacial  surface  temperatures  were  recorded  by  ocean  life 
the  temperatures  of  the  deep  sea  were  no  lower  than  their  coldest 
surface  temperatures.  Of  this  control  of  deep  sea  temperatures 
Professors  Chamberlin  and  Salisbury  say : 

The  deep  oceanic  circulation  is  now  dominated  by  polar  temperatures,  for 
it  is  the  cold  waters  of  the  polar  regions  that,  descending  and  flowing  towards 
the  equator,  control  the  temperatures  of  the  deep  sea.  This  is  now  low 
because  of  the  low  temperatures  of  the  polar  regions;  but,  if  the  circulation 
of  the  sub-carboniferous  and  carboniferous  periods,  whatever  its  nature  kept 
the  polar  regions  at  a  mild  temperature  the  great  body  of  the  deep  sea  must 
have  had  temperatures  correspondingly  higher,  and  the  water  must  have  had 
so  much  the  less  depressing  influence  on  the  temperatures  when  it  rose  to  the 
surface.  This  must  have  contributed  to  the  widespread  warmth  which  the 
sub-carboniferous,  and  perhaps  the  carboniferous  periods,  enjoyed.  The  mild- 
ness of  the  climates  in  these  and  several  other  periods,  before  and  since,  is  one 
of  the  most  remarkable  features  of  geologic  history.  The  crucial  feature  is 
the  maintenance  of  mild  temperatures  throughout  the  long  polar  night. 
Almost  the  only  approach  to  a  satisfactory  solution  seems  to  lie  in  a  warm 
ocean  circulation  blanketed  by  a  heat  retaining  atmosphere,  in  which  the  vapor 
of  water  and  carbon-dioxide,  abetted  by  a  prevalent  mantle  of  clouds,  generated 
by  warm  oceans,  conjoined  their  equalising  and  conservative  influences* 
Italicised  by  the  present  writer. 

1  Geology  Vol.  II,  pp.  658-659. 


32  THE   EVOLUTION    OF    CLIMATES 

If  this  were  true  for  sub-carboniferous  time,  it  must  also  have  been 
true  throughout  any  and  all  periods  during  which  mild  ocean  temper- 
atures prevailed.1 

It  is  therefore  held  that  the  mildness  of  geologic  climates,  although 
"  one  of  the  most  remarkable  features  of  geologic  history,"  is  con- 
firmed by  "  the  maintenance  of  mild  temperatures  throughout  the 
long  polar  night ;  "  and,  although  tropical  land  areas,  exposed  to  cold 
anti-cyclonic  winds,  were  severely  glaciated  in  Permo-Carboniferous 
time,  these  deep  and  prolonged  glaciations  were  possible  only  with 
warm  oceans,  which  alone  can  generate  sufficient  water  vapor  for 
glaciations,  and,  at  the  same  time  maintain  the  essential  cloud 
density  to  shield  them  from  solar  energy,  and  in  these  anti-cyclonic 
latitudes  the  cold  outer  air  first  zonally  descended  to  the  surface  as 
the  spheroidal  isotherms  shrank  towards  the  cooling  surface  of  the 
earth. 

THE  OCEAN    TEMPERATURES   OF   PLEISTOCENE   TIME 

For  the  first  time  in  geologic  history  ocean  life  recorded  the  com- 
plete chilling  of  the  oceans  in  Pleistocene  time,  and,  the  cloud  sphere 
manifestly  became  impaired  in  latitudes  of  maximum  cloud  density 
and  precipitation.  Glaciation  reached  its  maxima  under  the  rain 
belts  of  maximum  cyclonic  activities  in  middle  latitudes  and  extended 
into  polar  regions. 

The  loads  of  glacial  ice  in  these  latitudes  again  disturbed  isostasy, 
depressed  the  crust  under  the  weight  of  glacial  ice  of  a  maximum 
depth  of  more  than  a  mile  or  4.5  (io)10  tons  per  square  mile.  As 
the  cloud  sphere  in  these  latitudes  fluctuated  in  efficiency  with  fluctu- 
ating ocean  temperatures  and  these  depended  upon  the  liberation  oi 
increments  of  earth  heat,  the  alternation  of  conditions  favorable  01 
unfavorable  to  glaciation  in  these  regions  ensued.  Each  failure  of 
increments  of  earth  heat  to  maintain  the  integrity  of  the  cloud  sphere 
admitted  the  deglaciating  effects  of  solar  radiation,  until  effective 
increments  of  liberated  earth  heat  brought  the  oceans  above  the 
critical  temperature  of  generating  the  water  vapor  to  restore  the 
cloud  sphere  temporarily  in  these  regions  of  its  maximum  density, 
glaciation  was  thus  temporarily  reimposed. 

When  the  oceans,  chilled  to  their  maximum  degree,  and  no  longer 
yielded  water  vapor  in  sufficient  quantity  to  maintain  the  cloud 
sphere  in  any  latitude — any  further  heating  became  dependent  upon 

1  See  also  the  views  of  Svante  Arrhenius.  The  Destinies  of  the  Stars, 
pp.  89-91.  Also  the  description  of  moisture  and  clouds  when  quite  persistent, 
by  Hann,  as  quoted  by  Arrhenius,  pp.  86-88  of  work  just  cited. 


MARSDEN    MANSON  33 


surface  exposure  to  solar  radiation.1  This  exposure  does  not  gen- 
erate sufficient  water  vapor  to  sustain  glaciation  in  even  polar  lati- 
tudes, where  it  is  yet  retreating  according  to  the  high  authorities  who 
have  explored  these  regions  and  are  referred  to  herein. 

THE     CRITICAL     OCEAN     TEMPERATURES     IN    THE     MAINTE- 
NANCE OF  THE  CLOUD   SPHERE   IN  VARIOUS  ZONES 

As  cloudiness  is  disposed  in  zones  of  greater  or  less  density,  and 
as  the  cloudiness  in  each  zone  is  dependent  for  its  maintenance  upon 
the  amounts  of  water  vapor  generated  from  the  oceans,  there  neces- 
sarily follows  in  cooling  oceans  two  critical  periods  in  the  mainte- 
nance of  the  integrity  of  the  cloud  sphere:  (i)  That  degree  which 
would  just  maintain  this  integrity  in  zones  of  minimum  cloudiness, 
and  (2)  a  lower  degree  which  would  just  maintain  this  integrity  in 
zones  of  greater  cloud  density.  Now,  at  either  degree  a  compara- 
tively slight  chilling  of  the  oceans  would  check  the  generation  of 
water  vapor  and  reduce  the  cloudiness  in  the  particular  zone  affected, 
and  a  slight  rewarming  would  restore  it ;  or,  when  that  degree  which 
just  maintained  continuous  cloudiness  in  15°  to  35°  North  and  South 
latitude  was  reached  a  slightly  lower  degree  would  impair  the  integ- 
rity of  the  cloud  sphere  in  these  latitudes  and  expose  the  surfaces 
beneath  to  direct  solar  energy.  Under  these  conditions  of  control 
loading  and  unloading  of, more  quickly  cooling  and  rewarming  con- 
tinents disturbed  isostasy  to  such  extents  that  crustal  ruptures  fol- 
lowed. Earth  heat  thus  liberated  would  raise  the  ocean  temperatures 
slightly  above  the  critical  point  and  sufficient  water  vapor  would  then 
be  generated  to  restore  the  integrity  of  the  cloud  sphere  in  the  regions 
of  least  cloud  density.  These  conditions  would  impose  reglaciation 
and  deglaciation  until  crustal  stability  was  attained  in  so  far  as  the 
alternate  glacial  loading  and  deglacial  unloading  of  these  latitudes 
would  accomplish  it,  and  account  for  the  interglacial  epochs  during 
Permo-Carboniferous  time. 

At  a  later  stage  of  cooling  the  oceans  reached  that  temperature 
which  just  maintained  the  integrity  of  the  cloud  sphere  in  the  zones 
of  greater  cloud  density  of  middle  and  polar  latitudes.  The  more 
easily  chilled  continents  would  then  have  received  their  loads  of 
glacial  ice.  These  likewise  caused  ruptures  liberating  heat  and  warm- 
ing the  oceans,  thus  increasing  or  restoring  glaciation  until  the  oceans 
fell  to  slightly  lower  temperatures  than  would  maintain  cloudiness  in 

1  Unless  in  some  cataclysm  the  liberation  of  earth  heat  should  rewarm  the 
oceans  from  the  bottom,  when  geologic  climates  would  be  reinaugurated. 


34  THE   EVOLUTION    OF    CLIMATES 

these  latitudes,  and  glaciations  were  exposed  to  the  deglaciating 
power  of  solar  energy.  The  repeatedly  disturbed  isostasy  manifestly 
had  its  effects  and  crustal  ruptures  distinctly  recorded  the  liberation 
of  increments  of  earth  heat  with  the  resultant  acquistion  and  storage 
of  heat  by  the  oceans  and  the  re-establishment  of  the  integrity  of  the 
cloud  sphere  and  reglaciation  in  these  latitudes.  This  process  was 
manifestly  repeated  in  the  reglaciations  and  deglaciations  of  these 
latitudes  until  crustal  stability  checked  the  outbreak  of  farther  in- 
crements of  earth  heat  and  the  chilled  oceans  of  late  Pleistocene  time 
ceased  to  yield  sufficient  water  vapor  to  maintain  the  integrity  of  the 
cloud  sphere  in  all  latitudes.  This  variation  of  ocean  temperatures 
at  the  critical  stage  of  denser  cloud  formation  accounts  for  the  glacia- 
tions and  deglaciations  or  interglacial  epochs  during  Pleistocene  time. 
In  the  interim  between  these  two  great  glaciations  it  is  probable 
that  solar  control  prevailed  in  tropical  latitudes ;  and  that  the  chill 
of  Pleistocene  glaciation  was  felt  in  these  latitudes  only  by  a  marked 
lowering  of  the  snow  line.1 

EFFECTS  OF  SOLAR  RADIATION  DURING  THE  PREVALENCE  OF 

WARM  OCEANS2 

The  outer  media  "  the  true  radiating  surface  of  earth  as  a  planet  " 
and  the  cloud  sphere  during  its  maintenance,  received  and  utilized 
or  reflected  and  radiated  the  full  power  of  solar  radiation.  A  small 
fraction  of  the  energy  in  the  spectrum  niters  through  clouds  of 
moderate  density;  but  this  fraction  does  not  maintain  temperatures 
above  o°  Cent. 

The  fraction  of  solar  energy  not  reflected  by  the  high  albedo  of 
clouds  was  utilized  as  a  conservator ;  and  part  of  that  reflected  and 
radiated  was  further  conserved  by  the  atmosphere  beyond  this 
reflecting  surface. 

1  The  author  is  inclined  to  the  opinion,  based  upon  the  descriptions  of  others 
and  the  small'  areas  accurately  mapped  in  the  equatorial  zone,  that  this  zone 
of  maximum  cloud  density  was  more  heavily  glaciated  in  Pleistocene  time  than 
is  at  present  recognized.     Topography  in  this  zone  is   so  masked   in   dense 
forests  and  undergrowth  and  the  modifying  effects  of  torrid  heat  and  heavy 
rains  have  obscured  the  evidence,  if  there  be  such,  to  a  greater  degree  than 
elsewhere.     Dr.   Branner's    description   of   the  existence  of  the   remains   of 
gigantic  mammals  mixed  with  cobbles  and  boulders  in  the  swamps  of  equatorial 
Brazil,3  and  the  topographic  forms  on  the  southerly  edge  of  the  Sahara  and 
the  northerly  edge  of  the  Kalahari  Desert  mark  these  as  fruitful  fields  of 
research. 

2  Hilgard.    International  Geol.  Cong.,  Mexico,  1906. 

3  Trans.  Am.  Phil.  Society,  Vol.  XVI.  N.  S.,  pp.  421-422. 


MARSDEN    MANSON  35 

So  long  as  oceans  remained  warm  enough  to  maintain  the  integrity 
of  the  cloud  sphere  continents  would  be  protected  from  the  direct 
effects  of  solar  radiation,  at  any  temperature  they  might  reach. 
Whenever,  from  elevation,  remoteness  from  ocean  influences,  from 
exposure  to  anti-cyclonic  cold  winds  or  as  the  final  loss  of  earth- heat 
approached  in  Pleistocene  time,  continental  areas  fell  below  o°  Cent, 
conditions  favorable  to  glaciation  would  be  imposed,  namely,  cold 
continental  areas,  warm  oceans  and  the  interception  of  solar  radiation. 

Glaciation  under  these  conditions  could  be  checked  only  from  one 
or  the  other  source  of  heat,  by  the  liberation  of  effective  increments 
of  earth  heat,  or  by  the  further  chilling  of  the  oceans  to  such  a 
degree  as  to  check  the  generation  of  water  vapor  to  the  temporary 
or  permanent  impairment  of  the  efficiency  of  the  cloud  sphere,  thus 
letting  into  the  enclosing  constant  temperature  chamber  of  moist  air 
and  clouds  the  effects  of  the  powerful  and  practically  constant  source, 
solar  radiation. 

Now  this  source  at  present  fixes,  and  throughout  geologic  time 
fixed  the  zones  of  maximum  and  minimum  barometric  pressure,  the 
corresponding  distribution  of  anti-cyclonic  and  cyclonic  circulation, 
minimum  and  maximum  zones  of  cloudiness  and  precipitation.  This 
anti-cyclonic  circulation  was  the  reciprocal  circulation  of  that  in  the 
cyclonic  regions  and  this  circulation  was  the  principal  mode  of  pass- 
ing warm,  moist  air  through  the  cloud  sphere,  and  returning  cold 
air,  rain  and  snow  therefor. 

When  the  oceans  ceased  to  generate  sufficient  water  vapor  to  main- 
tain the  heat-intercepting  cloud  sphere,  it  yielded  first  in  the  anti- 
cyclonic  zones  of  least  cloudiness,  in  which  continents  of  lower 
specific  heat  had  been  previously  glaciated  under  the  effects  of  cold 
snow  laden  anti-cyclonic  winds.  The  balance  between  oceans  cold 
enough  to  generate  sufficient  or  insufficient  water  vapor  to  maintain 
the  integrity  of  this  cloud  sphere  is  a  delicate  one,  and  the  concen- 
trated loads  of  glacial  ice  laid  down  in  these  zones  disturbed  the 
isostasy  previously  existing.  These  loads  probably  depressed  and 
ruptured  the  crust  until  isostasy  was  restored,  to  be  again  disturbed 
upon  the  melting  of  the  load  and  its  distribution  evenly  over  the 
ocean  floors.  That  these  disturbances  ruptured  the  crust,  liberated 
increments  of  earth  heat  which  in  turn  were  gradually  lost  and  the 
process  probably  repeated  several  times,  is  noted  in  two  ways — 1st  by 
the  record  of  the  dislocations  and  crustal  ruptures  known  to  have 
taken  place ;  and  2nd  by  the  alternation  of  earth  heat  glaciations  and 
solar  heat  deglaciations  of  the  interglacial  epochs  which  mark  both 
Permo-Carboniferous  and  Pleistocene  glaciations. 


36  THE   EVOLUTION    OF    CLIMATES 

That  regions  outside  of  these  zones  of  anti-cyclonic  cold  winds 
and  of  least  cloudiness  were  not  exposed  to  glaciation  is  recorded  in 
the  fossil  forms  of  temperate  life  throughout  polar  and  temperate 
latitudes. 

The  ocean,  during  the  periods  succeeding  this  great  glaciation  of 
tropical  latitudes,  were  notably  uniform  in  temperature  distribution 
to  Pliocene  time.  Two  marked  periods  of  cold  continental  conditions 
marked  the  divisions  of  the  Mesozoic-Era :  one  between  the  Triassic 
and  Jurassic,  when  ruptures  of  the  crust  seem  to  have  restored 
ocean  temperatures  sufficiently  to  supply  the  water  vapor  for  quite 
extensive  glaciations ;  the  other  depression  in  continental  tempera- 
tures was  between  upper  Cretacic  and  Eocene  time,  when  vast  and 
successive  outpourings  of  lava,  each  at  least  200,000  square  miles  in 
area  and  several  miles  thick,  were  laid  down  on  the  weakest  portions 
of  the  North  American  and  Asian  land  masses.  These  great  lava 
plains  occupy  median  positions  on  the  two  land  masses  of  the  North- 
ern Hemisphere,  and  the  meridians  bisecting  them  are  almost  in  the 
same  plane. 

The  heat  from  the  Columbian  lava  plain  yet  makes  itself  manifest 
in  insignificant  outbursts  in  Yellowstone  Park,  but  was  an  efficient 
agency  in  protecting  the  "  Unglaciated  Area  "  and  in  checking  the 
southerly  flow  of  the  various  invasions  of  ice  in  the  great  glaciations 
of  Pleistocene  time,  which  reached  their  maxima  under  and  flowed 
from  the  North  temperate  rain  belt. 

During  the  two  cold  periods  in  the  interval  between  the  great  or 
zonal  glaciations  the  progressive  chilling  of  the  continents  was  noted 
by  the  retreat  of  land  animals  to  the  oceans,  where  they  became 
permanently  marine  in  habit,  and  by  the  cold  temperate  oceans  of 
the  Pliocene.1 

CONTROL  OF  GLACIATIONS  AND  DEGLACIATIONS— EFFECT  OF 

CLOUDS  DURING  THE  PREVALENCE  OF  THE  TWO 

SOURCES  OF  HEAT 

Under  the  interpretation  herein  rendered,  glaciations  and  deglacia- 
tions  were  dependent  upon  the  maintenance  and  impairments  of  the 
cloud  sphere,  which  in  turn  were  dependent  upon  ocean  temperatures, 
and  upon  the  liberation  of  earth  heat. 

Fluctuations  in  the  heat  stored  in  the  oceans  due  to  the  effects  of 
successive  increments  of  earth  heat  and  their  gradual  exhaustion 
would  cause  corresponding  variations  in  the  generation  of  water 
vapor  and  thus  cause  variations  in  the  integrity  of  the  cloud  sphere. 

1  Chamberlin  and  Salisbury,  Geology,  Vol.  Ill,  pp.  45,  185  and  239. 


MARSDEN    MANSON  37 

When  the  oceans  chilled  to  that  degree  which  began  to  impair  the 
integrity  of  the  cloud  sphere  this  impairment  would  take  place  first 
in  regions  of  least  cloudiness,  namely,  the  regions  of  maximum 
barometric  pressure  and  of  cold  anticyclonic  winds ;  next  in  regions 
of  greater  cloud  density ;  the  final  stage  being  when  the  oceans  lost 
the  last  effective  increment  of  earth  heat  and  became  dependent  upon 
exposure  to  solar  radiation  as  a  source  of  heat  and  further  evapor- 
ation. 

This  exposure  is  manifestly  not  capable  of  warming  the  surface  of 
the  oceans  to  a  sufficient  degree  to  generate  adequate  water-vapor  to 
maintain  glaciation  in  any  latitude  and  it  has  been  and  is  decreasing 
in  all  latitudes.  In  the  greater  or  zonal  glaciations  this  retreat  was 
fluctuating  by  reason  of  the  causes  and  conditions  elsewhere  discussed. 

Under  these  conditions  variations  in  the  temperatures  of  the 
oceans  would  impose  four  (4)  distinct  stages  ia  the  integrity  and 
efficiency  of  the  cloud  sphere : 

(1)  Periods  during  which  ocean  temperatures  were  sufficiently 
high  to  generate  water  vapor  in  adequate  quantity  to  maintain  the 
efficiency  of  the  cloud  sphere  in  all  latitudes.    These  periods  in  the 
aggregate  covered  the  greater  part  of  geologic  time,  through  which 
tropical  and  warm  temperate  oceans  and  non-zonal,  generally  humid 
climates  prevailed.1 

During  long  intervals  between  successive  increments  of  ocean 
stored  heat  continents  might  fall  quite  markedly  in  temperature  and 
glaciations  ensue  in  any  latitude,  notably  upon  continents  remote 
from  ocean  influences,  under  exposures  to  anticyclonic  activities,  and 
in  elevated  regions.  Deglaciation  would  result  from  additional  in- 
crements of  earth  heat  or  possibly  from  temporary  impairments  of 
the  cloud  sphere  as  under  (2). 

(2)  Periods   during  which   milder  oceans  generated  insufficient 
water  vapor  to  maintain  the  integrity  of  the  cloud  sphere  in  regions 
of  minimum  cloudiness  or  over  continents  and  in  the  zones  of  anti- 
cyclonic  activities  between  15°  and  35°  North  and  South  latitude. 
Before  this  stage  could  be  reached  continents  in  these  latitudes  would 
have  been  deeply  glaciated  by  reason  of  their  lower  specific  heat,  ex- 
posure to  cold  anti-cyclonic  winds,  and  being  protected  from  solar 
radiation  by  clouds  maintained  by  an  abundance  of  water  vapor  from 
the  still  warm  oceans.    They  would  be  deglaciated  by  impairments  of 
the  cloud  sphere  as  above.    Or,  at  this  critical  stage  of  cloud  main- 
tenance in  regions  of  least  density  they  would  fluctuate  between  con- 

1  White  and  Knowlton.    SCIENCE  N.  S.,  Vol.  XXXI,  p.  360. 


38  THE   EVOLUTION    OF    CLIMATES 

ditions  of  exposure,  alternately  favorable  or  unfavorable  to  glacia- 
tion.  Regions  of  low  barometric  pressure,  or  cyclonic  regions  of 
maximum  cloudiness,  would  not  at  that  time  be  exposed  to  such 
glaciation,  as  the  winds  reaching  them  would  be  warm  cyclonic  and 
not  cold  anti-cyclonic. 

(3)  Periods  during  which  still  colder  oceans  generated  insufficient 
water  vapor  to  maintain  the  integrity  of  the  cloud  sphere  in  regions 
of  more  persistent  cloudiness,  or  under  the  temperate  rain  belts  and 
in  polar  regions. 

This  stage  would  follow  a  more  extended  chilling  of  continents 
when  glaciation  of  regions  least  exposed  to  cold  winds  would  have 
reached  their  maxima.  Deglaciation  would  follow  impairments  in 
the  cloud  sphere  in  these  regions. 

Glaciations  in  regions  of  least  cloudiness  would  not  be  very  ex- 
tensive for  in  them  a  greater  impairment  of  the  cloud  sphere  would 
have  taken  place,  and  greater  or  even  permanent  exposure  of  these 
regions  to  solar  radiation  would  have  been  previously  imposed. 

Glaciations  under  these  conditions  manifestly  reached  maxima  at 
different  latitudes  at  different  periods,  that  is,  maxima  were  imposed 
first  in  the  latitude  of  the  tropics,  by  reason  of  the  maximum  anti- 
cyclonic  circulation  of  these  latitudes,  which  brought  the  cold  of  space 
to  the  slowly  cooling  surface;  then,  upon  the  final  chilling  of  Pleisto- 
cene time  maxima  were  imposed  in  the  belts  of  maximum  precipita- 
tion ;  and  finally,  as  deglaciation  progressed  polar  regions  were  left  as 
apparent  maxima  by  reason  of  being  least  exposed  to  solar  energy. 

In  Pleistocene  deglaciation  temperate  latitudes  may  have  been  de- 
glaciated  before  maxima  had  been  reached  in  polar  latitudes.  These 
latter  maxima  have  been  reached  and  permanent  deglaciation  is 
progressing. 

(4)  The  final  or  permanent  stage ;  during  which  greater  crustal 
stability  having  been  attained  and  effective  increments  of  earth  heat 
are  no  longer  received  by  the  oceans,  they  have  chilled  to  their  lowest 
degree,  and  have  ceased  to  generate  sufficient  water  vapor  to  main- 
tain the  efficiency  of  the  cloud  sphere  or  to  maintain  glaciations  at 
any  latitude.    During  this  stage  only  about  52  per  cent  of  the  earth's 
surface  is  permanently  clouded. 

Solar  control  of  climates  under  this  stage  is  being  established, 
under  this  control  glaciation  does  not  occur — except  possibly  in 
some  remote  eon  of  stellar  evolution  when  solar  radiation  shall  de- 
cline. A  light  glaciation  from  cold  oceans  and  comparatively  clear 
skies  would  then  follow,  commencing  in  polar  regions.  Such  a 
glaciation  has  not  been  recorded  in  geologic  time. 


MARSDEN    MANSON  39 

It  will  be  noted  that  under  (2)  and  (3)  the  balance  may  have  been 
easily  turned  between  ocean  temperatures  capable  or  incapable  of 
generating  sufficient  water  vapor  to  maintain  the  integrity  of  the 
cloud  sphere  either  in  regions  of  least  or  later  in  regions  of  more 
persistent  cloudiness.  During  either  stage,  and  notably  in  (3), 
changes  in  the  topographic  form  of  the  earth's  crust,  whether  con- 
tinental or  submarine,  due  to  disturbances  of  its  isostasy  by  glacia- 
tions  and  deglaciations,  and  other  crustal  strains,  liberated  sufficient 
earth  heat  to  restore  milder  temperatures  both  on  land  and  in  oceans,1 
this  restored  the  cloud  sphere  and  again  intercepted  solar  radiation. 
These  increments  of  earth  heat  were,  in  time,  lost  on  continents 
earlier  than  by  oceans ;  and,  thus  imposed  an  alternation  of  control, 
which  caused  glaciation  and  deglaciation  in  either  of  the  great  glacia- 
tions,  and  accounts  for  interglacial  epochs  in  both  temperate  and  in 
tropical  latitudes.  Such  reglaciations  followed  deglaciations  caused 
by  temporary  or  short  period  exposures  to  solar  radiation  in  latitudes 
which  could  not  be  glaciated  under  this  latter  control.  Deglaciations 
were  generally  conformable  to  solar  control,  and  glaciations  and  re- 
glaciations were  non-conformable  to  such  control.  These  phenomena 
followed  one  another  at  such  short  intervals  that  they  could  not  be 
attributed  to  short  period  and  wide  variations  in  the  more  constant 
and  powerful  source,  solar  radiation.  They  belong  rather  to  exhaus- 
tions of  and  additions  to  available  increments  of  the  lesser  source — 
earth  heat — and  also  to  variations  in  ocean  temperatures  when  the 
balance  was  easily  turned  between  the  generation  of  a  sufficient  or 
an  insufficient  amount  of  water  vapor  to  maintain  the  efficiency  of 
the  cloud  sphere,  thus  causing  an  alternation  of  control. 

The  only  remaining  cause  of  the  order  of  decreasing  ice  loads  is 
the  gradual  unloading  of  polar  regions  of  their  remaining  glacial 
overloads  and  the  restorations  of  these  as  uniformly  distributed  loads 
to  the  ocean  bottoms.  This  may  cause  slight  elevations  of  polar  land 
areas  accompanied  by  corresponding  adjustments  to  the  equatorial 
bulge  imposed  by  axial  rotation. 

CONDITIONS  OF  GLACIATION 

Under  the  interpretation  of  geologic  climates  herein  offered,  gla- 
ciations were  possible  under  the  following  conditions : 

When  by  the  exhaustion  of  an*  increment  of  earth  heat  continents 
were  chilled: 

*That  such  disturbances  took  place  in  Pleistocene  time,  see  The  Great  Ice 
Age,  p.  790  (4th  Ed.),  Prof.  Jas.  Geikie. 


4O  THE   EVOLUTION    OF    CLIMATES 

(1)  By  reason  of  elevation  above  sea  level. 

(2)  By  reason  of  remoteness  from  ocean  influences. 

(3)  By  exposure  to  the  cold  of  anti-cyclonic  winds  in  latitudes  of 
their  greatest  activity. 

(4)  By  the  final  cold  at  the  approach  of  the  exhaustion  of  the  last 
effective  increments  of  earth  heat. 

The  zonal  control  of  cloud  occurrence  and  density  by  solar  energy, 
irrespective  of  the  source  of  heat  generating  the  water  vapor  essential 
for  their  existence  and  maintenance,  must  be  kept  fully  in  mind  ;  also 
the  fact  that  the  loci  of  the  zones  of  the  maximum  and  minimum 
influences  of  anti-cyclonic  and  cyclonic  winds  are  imposed  and  con- 
trolled by  the  same  source  of  energy,  and,  that  the  former  were  the 
regions  in  which  the  cold  of  the  upper  air  first  reached  the  surface 
and  produced  zonal  glaciations,  and  being  also  in  latitudes  of  least 
cloud  density,  the  cloud  sphere  must  have  been  here  first  impaired. 
Land  areas  in  each  of  these  zones  chilled  prior  to  the  oceans  and 
were  therefore  exposed  to  glaciation.  Furthermore  in  cooling  oceans 
each  of  these  impairments  occurred  at  a  critical  temperature;  first 
that  degree  which  could  just  maintain  cloud  density  in  the  zones  of 
minimum  cloudiness ;  and  lastly,  that  degree  which  could  just  main- 
tain cloudiness  in  the  zones  of  maximum  cloud  density.  Moreover, 
if,  during  the  existence  of  either  glaciation,  the  oceans  should  fluctu- 
ate in  temperature  to  points  somewhat  above  or  somewhat  below 
these  critical  temperatures,  corresponding  variations  in  the  generation 
of  water  vapor  would  necessarily  follow,  imposing  variations  in  the 
integrity  of  the  cloud  sphere  in  each  latitude.  Each  fall  below  this 
critical  temperature  would  impair  the  cloud  sphere,  and  each  rise 
above  this  temperature  would  restore  it,  thus  alternately  exposing 
the  surface  to  solar  energy  and  shutting  off  the  same  until  the  oceans 
again  chilled  below  the  critical  temperature. 

Severe  zonal  glaciation  was  therefore  first  imposed  in  the  zones  of 
maximum  anti-cyclonic  circulation  of  cold  air  which  glaciated  the 
land  areas  so  exposed.  Further  chilling  exhausted  ocean  stored 
earth  heat  below  the  critical  temperature  necessary  to  maintain  the 
cloud  sphere  in  these  latitudes  of  least  density  and  partial  deglacia- 
tion  followed  from  exposure  to  solar  energy.  Consequent  disturbed 
isostasy  and  resultant  crustal  ruptures,  with  liberation  of  earth  heat, 
restored  the  oceans  to  a  few  degrees  above  the  critical  temperature 
and  thus  restored  the  cloud  sphere  in  these  latitudes  with  its  inter- 
ceptions of  solar  energy.  Repetitions  of  these  actions  and  reactions 
followed  until  crustal  stability  was  attained  in  these  latitudes  in  so 


MARSDEN    MANSON  41 

far  as  their  loading  by  glaciation  and  unloading  by  deglaciation 
would  bring  about  this  result. 

In  the  same  manner  as  the  final  chill  of  complete  loss  of  earth  heat 
approached,  middle  latitudes  of  maximum  precipitation  and  cloud 
density,1  were  zonally  glaciated  and  deglaciated  as  in  the  zones  of 
least  cloud  density. 

Upon  the  establishment  of  crustal  stability  in  the  temperate  zones 
of  cloud  belts  and  rains  ocean  stored  earth  heat  ceased  to  be  replen- 
ished by  ruptures,  and  ocean  temperatures  fell  below  the  critical 
temperatures  which  yields  sufficient  water  vapor  to  maintain  the 
cloud  sphere  in  regions  of  its  greatest  density.  Permanent  deglacia- 
tion followed,  and  is  yet  progressing  in  polar  latitudes  of  least  solar 
efficiency. 

Zonal  glaciation  was  thus  first  imposed  in  tropical  latitudes  by 
reason  of  exposure  to  the  zonally  disposed  anti-cyclonic  winds  of 
those  latitudes ;  it  was  zonally  disposed  in  temperate  latitudes  by 
reason  of  these  being  the  zones  of  the  temperate  rain  belts.  The 
deglaciation  of  each  of  these  latitudes  was  effected  by  solar  energy 
admitted  to  the  surface  as  the  cloud  sphere  failed  first  in  tropical 
and  later  in  middle  latitudes.  Interglacial  epochs  were  imposed  upon 
each  of  these  latitudes  under  the  same  conditions,  namely,  fluctua- 
tions of  ocean  temperatures  as  their  stored  heat  was  lost  and  restored 
between  crustal  ruptures  when  at  critical  temperatures  of  cloud  main- 
tenance either  in  zones  of  minimum  or  of  maximum  cloud  density. 

Crustal  ruptures  were  caused  at  these  critical  stages  by  reason  of 
alternate  overloading  by  glaciation,  and  unloading  by  deglaciation, 
thus  transferring  an  evenly  distributed  load  upon  ocean  bottoms  to 
continents  as  an  unevenly  distributed  load,  which,  from  its  low 
viscosity  accumulated  to  depths  of  over  a  mile,  imposing  crustal  loads 
of  over  4^  billion  tons  per  square  mile. 

SUMMARY  OF  THE  CAUSES  AND  CONDITIONS  OF  GLACIATIONS 
AND  DEGLACIATIONS,  AND  OF  INTERGLACIAL  EPOCHS 

Under  these  conditions  glaciations  were  the  result  of  the  chilling 
of  continental  areas  to  or  below  o°  Cent,  while  the  oceans  were  still 
warm.  The  two  conditions  essential  for  glaciation  are — (i)  Cold 
Continental  Areas — cold  from  more  rapid  chilling  where  remote 
from  ocean  influences,  from  elevation,  from  exposure  to  cold  anti- 
cyclonic  winds,  and,  upon  the  final  loss  of  effective  earth  heat; 

1  Probably  also  equatorial  latitudes  under  the  belt  of  clouds  and  greater 
precipitation  in  that  zone.  See  note  i,  p.  34. 


42  THE   EVOLUTION    OF    CLIMATES 

(2)  Warm  Oceans,  to  supply  water  vapor  in  sufficient  amounts  to 
deeply  glaciate  and  to  maintain  continuous  cloudiness  to  intercept 
solar  energy. 

There  were  under  the  causes  and  conditions  which  determine  the 
integrity  of  the  cloud  sphere  three  types  of  glaciation : 

(1)  Glaciations  occurring  upon  exposed  continental  areas  in  any 
latitude,  particularly  areas  remote  from  ocean  influences  and  after 
a  long  period  of  crustal  stability ;  such  areas  were  subject  to  deglacia- 
tion  either  by  exposure  to  solar  energy  by  temporary  impairments 
of  the  cloud  sphere  or  by  an  accession  of  effective  heat  from  crustal 
rupture.1 

(2)  Glaciations  due  to  exposure  to  cold  anti-cyclonic  winds  which 
reached  the  surface  to  maximum  extents  in  the  latitudes  between 
15°  and  35°  North  and  South,  which  latitudes  are  regions  of  least 
cloud  density.     This  is  a  critical  stage  in  ocean  temperatures,  for 
having  reached  a  temperature  just  capable  of  yielding  sufficient  water 
vapor  to  maintain  cloudiness  in  these  regions  of  least  cloud  density 
a  slight  fall  would  impair  this  density  and  expose  the  surface  to  the 
effects  of  a  tropical  sun ;  crustal  rupture  at  this  stage  of  disturbed 
isostasy  would  temporarily  rewarm  the  oceans  and  restore  the  cloud 
sphere  in  these  latitudes  with  resulting  temporary  reglaciation,  to  be 
followed  by  the  permanent  deglaciation  of  tropical  latitudes. 

(3)  Glaciations  due  to  the  final  checking  of  ruptures  of  the  crust 
as  it  approached  its  present  stability  and  ceased  thereby  to  release 
increments  of  earth  heat. 

This  is  also  a  critical  stage  in  ocean  temperatures  and  in  cloudiness 
in  regions  of  greater  cloud  density — slight  ocean  fluctuations  at  this 
stage  would  impose  conditions  alternately  favorable  to  glaciation  and 
deglaciation  in  these  regions  or  result  in  the  interglacial  epochs  of 
temperate  latitudes. 

Final  deglaciation  was  inaugurated  at  the  culmination  of  Pleisto- 
cene glaciation  or  the  Ice  Age,  and  after  the  interglacial  fluctuations, 
and  is  yet  progressive  in  polar  latitudes. 

When  we  review  the  cumulative  effects  of  this  rewarming;  the 
deglaciation  of  millions  of  square  miles  of  continental  areas  and  the 
establishment  thereon  of  conditions  suitable  for  man's  highest  de- 
velopment— the  rewarming  of  the  surface  of  the  oceans  in  middle 
latitudes — the  progressive  deglaciation  of  polar  wastes,  we  have  a 
better  mental  grasp  of  the  work  of  that  fraction  of  solar  radiation 
which  now  reaches  the  surface  of  the  planet ;  and  also  of  its  conserv- 

1  Huronian  and  Cretacic  glaciations  are  elsewhere  cited  as  types  of  this  class. 


'   MARSDEN    MANSON  43 

ative  effects  when  a  large  fraction  of  its  power  was  intercepted  by 
clouds  maintained  by  the  cooling  crust  and  heat  storing  oceans.  The 
limits  of  this  increase  are  moderate  for  the  heating  of  the  oceans  is 
checked  by  increasing  evaporation  and  cloudiness,  and  the  impos- 
sibility of  warming  the  cold  depths  of  the  ocean  from  surface  ex- 
posure is  a  permanent  check  upon  any  future  rise  in  mean  tempera- 
ture beyond  very  moderate  limits. 

CLASSIFICATION    OF    GLACIAL     PERIODS,     DEGLACIATIONS,    AND    INTER- 
GLACIAL   EPOCHS 

We  may  therefore  classify  and  define  glacial  periods  in  accordance 
with  the  special  conditions  under  which  they  occurred : 

(1)  Non-Zonal  or  Minor  Glacial  Periods  were  such  as  occurred 
both  before  and  after  Permo-Carboniferous  time.     Those  occurring 
before  this  period  were  widely  distributed  in  latitude  and  dependent 
upon  remoteness  from  ocean  influences  and  upon  elevation ;  Huron- 
ian  glaciation  may  be  taken  as  a  type.     Those  subsequent  thereto 
were  due  to  the  same  causes  but  prevailed  principally  in  temperate 
and  equatorial  latitudes  and  possibly  extended  to  polar,  the  glacia- 
tion at  the  close  of  the  Cretacic  may  be  taken  as  a  type.    Glaciations 
in  tropical  latitudes  subsequent  to  Permo-Carboniferous  time  were 
apparently  confined  to  elevated  areas. 

(2)  Zonal  Glaciations  or  Major  Glacial  Periods  were: 

(A)  In  the  zones  of  exposure  to  cold  anti-cyclonic  winds  ; 

(B)  In  the  zones  of  maximum  precipitation  and  cloudiness  which 
were  glaciated  upon  the  ultimate  failure  of  earth  heat. 

Deglaciation. — Deglaciations  of  non-zonal  or  minor  glaciations 
were  apparently  caused:  (i)  By  the  increase  of  temperature  inside 
the  constant  temperature  chamber  of  moist  air  and  clouds  by  earth 
heat  which  was  liberated  by  crustal  ruptures  etc.,  these  were  in  part 
caused  by  overloads  of  glacial  ice  upon  the  forming  crust ;  (2)  by 
temporary  impairments  of  the  cloud  sphere  over  continents. 

Deglaciation  of  tropical  latitudes  in  Permo-Carboniferous  time 
was  caused  by  exposures  to  solar  energy  by  reason  of  the  failure  of 
the  cloud  sphere  in  these  regions  of  least  cloud  density. 

Deglaciation  at  the  close  of  Pleistocene  time  was  caused  by  the 
final  loss  of  ocean  stored  heat  and  the  reduction  of  oceans  to  that 
temperature  which  generated  less  water  vapor  than  is  required  to 
maintain  the  integrity  of  the  cloud  sphere  in  all  latitudes ;  this  per- 
manently exposed  the  surface  to  the  deglaciating  power  of  solar 
energy  under  which  no  glaciation  has  been  recorded.  Fluctuations 
in  ocean  temperatures  during  either  of  these  critical  stages  would 


44  THE   EVOLUTION    OF    CLIMATES 

cause  alternations  of  control  between  the  two  sources ;  a  temporary 
local  failure  of  the  cloud  sphere  would  cause  deglaciation  by  exposure 
to  solar  energy,  and  a  slight  rise  in  ocean  temperature  would  restore 
the  cloud  sphere  and  leave  the  surface  temperatures  to  the  fading 
effects  of  earth  heat.,  or  would  cause  reglaciation. 

Inter-Glacial  Epochs  were  therefore  caused  by  fluctuations  in 
ocean  temperatures  during  zonal  glaciations,  and  in  these  phenomena 
are  recorded  the  alternation  of  control  between  the  two  sources  of 
heat. 

The  last  major  glacial  period,  B,  may  well  be  termed  The  Ice  Age 
and  may  be  defined  as  follows : 

The  Ice  Age  was  the  period  just  antedating  the  final  loss  of  ocean 
stored  earth  heat  and  culminated  in  the  final  glaciation  of  land  areas 
in  latitudes  of  maximum  precipitation  and  cloud  density.1 

The  decline  of  The  Ice  Age  was  inaugurated  as  the  oceans  lost 
their  last  effective  increment  of  earth  heat  and  became  dependent  for 
any  increase  of  surface  temperature  upon  solar  energy,  under  which 
exposure  sufficient  water  vapor  is  not  generated,  either  to  maintain 
cloud  density  to  a  sufficient  extent  to  protect  glaciated  areas  or  to 
yield  winter  snowfall  equivalent  to  summer  melting. 

THE  ESTABLISHMENT  OF  SOLAR  CLIMATIC  CONTROL 

The  change  from  the  dual  effects  and  the  climatic  control  by  earth 
heat  to  that  by  solar  energy  alone  was  so  important  a  development 
in  the  evolution  of  climates  that  it  is  best  to  review  briefly  the 
author's  interpretation  of  the  conditions  and  stages  of  this  change. 

It  was  not  effected  during  any  one  period,  nor  in  all  latitudes 
coincidently.  It  was  inaugurated  just  after  the  culmination  of  the 
zonal  glaciation  of  tropical  latitudes  in  Permo-Carboniferous  time; 
and,  after  short  alternations  of  control,  as  heretofore  explained, 
ocean-stored  earth  heat  ceased  to  yield  sufficient  water  vapor  to  re- 
establish and  to  maintain  the  cloud  sphere  in  the  tropical  regions  of 
its  least  density ;  this  permitted  a  fraction  of  solar  radiation  to  reach 
the  surface  in  these  latitudes  and  thereafter  to  dominate  their 
climates. 

So  far  as  the  author  understands  the  geologic  records,  climatic 
control  by  earth  heat  was  not  re-established  in  the  tropical  regions, 
for  this  would  have  required  the  rewarming  of  the  oceans  to  that 

1  F.  W.  Harmer,  F.  G.  S.,  has  discussed  "  The  influence  of  the  winds  upon 
climate  during  the  Pleistocene  epoch."  Quart.  Jour.  Geol.  Society,  Aug.,  1901. 
pp.  405-476. 


MARSDEN    HANSON  45 

' 

temperature  which  would  restore  the  cloud  shield  and  result  in  an- 
other similar  zonal  glaciation,  followed  by  an  alternation  of  control 
as  it  passed  away  under  clearing  tropical  skies,  and  permanent  solar 
control  of  the  climates  of  these  zones. 

These  complex  conditions — the  glaciation  and  deglaciation  of  trop- 
ical regions  under  the  zones  of  anti-cyclonic  circulation,  while  middle, 
polar  and  equatorial  regions'  under  cyclonic  circulation  remained 
mild,  present  what  Professors  Chamberlin  and  Salisbury  term  "  a 
plexus  of  problems  of  unparalled  difficulty."  Under  the  assumption 
of  solar  climatic  control  this  conclusion  is  preeminently  correct.  But 
these  problems  appear  to  present  somewhat  lighter  difficulties  and 
to  yield  under  the  interpretation  and  analysis  herein  essayed. 

During  the  long  interval  from  and  including  the  Triassic  to  the 
establishment  of  the  Modern  Era  of  complete  solar  climatic  control, 
the  two  sources  appear  to  have  coincidently  prevailed — the  greater, 
solar  energy,  in  the  tropical  zones,  in  which  the  integrity  of  the  cloud-3 
sphere  had  been  permanently  impaired ;  and,  the  lesser,  earth  heat, 
in  the  zones  of  denser  and  more  persistent  cloudiness  and  in  which  a 
lower  ocean  temperature  is  capable  of  maintaining  cloudiness  than  in 
the  zones  of  its  least  occurrence. 

During  the  greater  part  of  Triassic  time  widely  distributed  mild 
climates  prevailed,  but  at  its  close  the  gradual  loss  of  the  available 
increments  of  earth  heat  imposed  a  milder  glaciation  during  which 
certain  forms  of  land  life  deserted  the  more  readily  chilled  continents 
and  retreated  to  the  milder  oceans.  Tropical  zones  under  solar  con- 
trol offered  more  constant  mildness  and  in  these  a  larger  proportion 
of  life  survived. 

Under  the  influence  of  the  increments  of  earth  heat  which  were 
made  available  by  the  ruptures  near  the  close  of  the  Cretacic  mild 
conditions  were  partly  restored  in  regions  still  under  earth  heat  con- 
trol. This  mildness  again  gave  way  near  the  close  of  this  period, 
which  caused  a  second  permanent  migration  of  land  life  to  milder 
oceans. 

There  followed  the  temperate  climates  of  Eocene  and  Miocene 
time,  succeeded  by  the  cold  temperate  climates  of  the  Pliocene. 

Pleistocene  glaciation  succeeded,  it  marked  the  final  chilling  of 
lands,  and  oceans  chilled  to  a  degree  never  before  attained.  "  The 
whole  world  felt  its  effects."  The  great  zonal  glaciations  of  this 
period  reached  their  maxima  under  the  belts  of  maximum  pre- 
cipitation. 

The  two  great  zonal  glaciations  therefore,  reached  their  maxima 
tinder  different  conditions ;  both  were  imposed  under  earth  heat  con- 


46  THE   EVOLUTION   OF   CLIMATES 

trol,  but  tropical  glaciations  reached  their  maxima  under  the  anti- 
cyclonic  circulations  of  these  latitudes,  while  Pleistocene  glaciations 
reached  their  maxima  under  the  cyclonic  belts  of  maximum  precipi- 
tation; both  of  these  zonal  glaciations  fluctuated  between  partial 
deglaciations  and  re-glaciations  due  to  alternations  of  climatic  con- 
trol ;  and,  final  de-glaciation,  in  both  cases,  was  due  to  solar  control — 
the  earlier  as  the  cloud  shield  failed  in  its  least  dense  and  the  later  in 
its  densest  zones. 

Solar  control  now  completely  dominates  climates,,  even  in  the  great 
glaciated  areas  about  the  poles ;  and  these  and  ksser  residuals  of 
Pleistocene  glaciation  are  yet  slowly  and  finally  disappearing. 

THE    CLIMATIC    TRANSITION    ERA 

The  periods  between  the  culminations  of  the  two  major,  or  zonally 
disposed,  glaciations  constitute,  therefore,  a  climatic  transition  era. 
During  this  transition  the  two  sources  coincidently  prevailed  in 
different  zones.  The  cloud  sphere  having  first  permanently  failed  in 
the  zones  of  its  least  density  permitted  solar  radiation  to  reach  the 
surface  and  to  dominate  their  climate.  Under  the  belts  of  densest 
cloud  formation  the  climates  were  still  dominated  by  the  gradually 
failing  earth  heat,  which  as  its  final  exhaustion  approached  was  too 
feeble  to  maintain  continental  temperatures  above  o°  Cent. ;  their 
glaciation,  therefore,  followed,  reaching  maxima  under  the  zones  of 
maximum  precipitation.  Upon  the  final  chilling  of  the  oceans  and 
the  consequent  failure  of  the  cloud  sphere  in  its  densest  zones,  de- 
glaciation  under  solar  radiation  resulted,  and  this  source  remains  in 
the.  sole  control  of  climates. 


PART  II 

APPLICATION    OF   THE    PRINCIPLES   HEREIN    SET   FORTH   TO 
THE  FACTS  OF  PALEONTOLOGY  AND  GEOLOGY  AS  COM- 
PILED   AND    DISCUSSED    BY    PROFESSOR    CHARLES 
SCHUCHERT  IN  "CLIMATES  IN  GEOLOGIC  TIME" 

Professor  Schuchert's  review  and  presentation  of  the  facts  of 
Paleontology  and  Geology,  bearing  upon  climatic  variations  is  so 
accurate,  succinct  and  clear  that  it  is  well  adapted  and  lends  itself 
admirably  for  the  application  and  test  of  any  interpretation  of  the 
causes  and  conditions  which  controlled  Geologic  and  present  climates.1 
Although  these  facts  were  compiled  under  very  different  concep- 
tions of  the  causes  of  climatic  variations  than  is  herein  presented,  the 
author  elects  to  apply  the  principles  and  interpretation  herein  ren- 
dered to  Professor  Schuchert's  masterly  presentation. 

The  temperature  curve  and  the  periods  of  mountain  making,  or 
of  "  changes  in  the  topographic  form  of  the  earth's  surface,"  on  Pro- 
fessor Schuchert's  chart 2  are  reproduced  on  the  diagram  herewith. 
The  other  elaborate  data  expressed  on  this  chart  are  not  reproduced 
as  they  are  not  essential  to  the  author's  presentation  of  the  causes 
of  climatic  variations.  These  variations  would  have  occurred 
whether  the  strand  lines  of  continents  varied  or  remained  fixed, 
whether  coal  or  limestone  formed  or  not,  and  would  recur  if  crustal 
ruptures  should  liberate  sufficient  earth  heat  to  rewarm  the  oceans. 

This  temperature  curve  is  manifestly  intended  for  continental  vari- 
ations, but  ocean  temperatures  are  mentioned  throughout  the  text ; 
from  these  an  ocean  temperature  curve  is  added,  and,  both  curves  are 
extended  to  indicate  the  distributions  of  temperatures  during  the 
Modern  Era.  This  requires  separate  curves  to  express  the  mean 
yearly  temperatures  of  low,  middle  and  high  latitudes  as  neither  the 
existing  distribution  of  ocean  temperatures  nor  of  climates  conforms 
to  those  of  geologic  time. 

1  The  Climatic  Factor,  Dr.  Ellsworth  Huntington,  Publication  No.  192,  Car- 
negie Institution  of  Washington,  Smithsonian  Institution,  Report  1914,  pp. 
277-311. 

3L.  c.  p.  305- 

47 


MARSDEN    HANSON  49 

An  inspection  of  the  curve  of  continental  temperatures  shows  that 
there  were  thirteen  (13)  short-period  depressions,  as  follows: 

(1)  At  the  dazvn  of  Proterozoic  time. 

(2)  During  Proterozoic  time. 

(3)  Between  Proterozoic  and  Cambric  time. 

(4)  During  Middle  Cambric  time. 

(5)  Between  Middle  and  Upper  Ordovicic  time. 

(6)  Between  Upper  Ordovicic  and  Siluric  time. 

(7)  Between  Siluric  and  Devonic  time. 

(8)  Between  Devonic  and  Lower  Carbonic  time. 

(9)  BETWEEN  UPPER  CARBONIC  AND  PERMIC  TIME. 

(10)  Between  Triassic  and  Jurassic  time. 

( 1 1 )  Between  Jurassic  and  lower  Cretacic. 

(12)  Between  upper  Cretacic  and  Eocene. 

(13)  BETWEEN  PLIOCENE  AND  THE  MODERN  ERA. 

OCEAN  TEMPERATURES  DURING  GEOLOGIC   CLIMATES 

The  following  ocean  temperatures  are  noted  in  the  text  of  Profes- 
sor Schuchert's  review : 

Proterozoic  (p.  291).    "Warm  waters  teeming  with  life." 

Lower  Cambric  (pp.  283-4).  "  The  world  over  tropical  and  sub- 
tropical." 

Lower  Cambric  (p.  291).    "  Fairly  uniform  the  world  over." 

Early  Cambric  (p.  292).     "Relatively  mild." 

Ordovicic  and  Siluric  (pp.  292-3).    "  Mild  and  uniform." 

Devonic  (pp.  293-4).  Cooler  oceans  and  local  continental  glacia- 
tions. 

Middle  Devonic  (p.  294).    Warmer  conditions. 

Late  Devonic  and  Carboniferous  (p.  294-5).  World  wide  warm 
waters. 

Upper  Carbonic  (p.  295).  Relatively  uniform  and  mild,  sub-trop- 
ical in  places  and  extending  into  the  polar  circles. 

Permic  (p.  297).    Marine  life  much  like  that  of  the  coal  measures. 

Triassic  (p.  298).  Nearly  uniform  distribution  of  warm  waters 
over  a  great  part  of  the  globe. 

Between  late  Triassic  and  earliest  Jurassic  (pp.  298-9).  Cooler 
climates,  not  local  but  of  a  general  nature,  local  continental  glaciation. 

Middle  and  Upper  Jurassic  (p.  300).  Warm  throughout  the 
greater  part  of  the  world,  cooler  but  not  cold  waters  in  the  polar 
areas. 

Cretacic  to  Eocene  (p.  303).  No  marked  climatic  change  but  a 
reduction  in  temperature  marked  in  marine  life. 


5O  THE    EVOLUTION    OF    CLIMATES 

Middle  Miocene  (p.  303).    Temperate  waters,  Atlantic  and  Pacific. 

Late  Pliocene  (p.  304).    Polar  waters  were  cool. 

From  this  data  the  curve  of  ocean  temperatures  is  laid  out.1 

COMPARISON    OF    THE    CURVES    OF    CONTINENTAL    AND    OF    OCEAN 

TEMPERATURES 

These  curves  distinctly  mark  two  significant  facts : 

(1)  That  continents  fluctuated  between  tropical  and  glacial  tem- 
peratures, the  depressions  being  short  and  of  varying  intensity  with 
two  distinct  minima :  Between  upper  Carbonic  and  Permic  time,  (9), 
and,,  between  Pliocene  and  Recent  Time,  (13). 

(2)  That  oceans  fluctuated  between  more  moderate  limits,  and 
reached  glacial  temperatures  only  once  in  geologic  history,  namely : 
Near  the  close  of  Pleistocene  time. 

The  distinct  periods  of  zonal  glaciation  were  notably  different  in 
locality,  in  succession  and  significance:  The  earlier,  Permo-Carbon- 
iferous  time  (9),  was  preceded  and  succeeded  by  periods  of  univer- 
sally warm  climates,  and  was  accompanied  throughout  with  warm 
oceans.  The  glaciations  were  localized  in  the  zones  between  latitudes 
15°  and  35°  north  and  south,  or  they  occupied  the  north  and  south 
tropical  zones  of  minimum  cloudiness  and  rainfall  of  the  Modern 
Era.  Judged  by  depth  of  tillite  they  were  the  severest  recorded. 
They  gave  place  to  the  succeeding  widely  distributed  milder  condi- 
tions of  Triassic  time  after  a  series  of  deglaciations  and  reglaciations. 

The  last  Pleistocene  time  (13)  was  as  distinctly  localized  in  the 
middle  latitudes  of  the  temperate  rain  belts  of  the  Modern  Era,  and 
extended  into  polar  latitudes.  Both  middle  and  Polar  latitudes 
escaped  in  the  former  period  of  maximum  glaciation ;  or,  the  zones 
of  maximum  glaciations  in  either  period  escaped  in  the  other.  This 
glacial  period  was  preceded  by  the  cold  temperate  oceans  of  Pliocene 
time  when  "  polar  waters  were  cool  " ;  it  was  accompanied  by  glacial 
oceans,  in  middle  and  polar  latitudes,  and,  was  succeeded  by  the 
zonally  distributed  temperatures  of  today,  ranging  between  the  torrid 
climate  of  equatorial  latitudes  and  the  glacial  climate  of  polar  lati- 
tudes. It  merged  into  these  conditions  after  short  periods  of  degla- 
ciation  and  reglaciation  in  middle  latitudes,  gradually  receding  to  the 
progressive  deglaciations  of  polar  latitudes  and  the  upward  retreat 
of  the  snow  line  in  all  latitudes  and  a  rewarming  of  the  surface  of 
the  oceans  in  middle  latitudes,  which  is  greater  in  the  narrow 
Atlantic  than  in  the  broad  Pacific  ocean.  This  deglaciation  and  re- 

1  See  Also  White  and  Knowlton.    SCIENCE,  N.  S.,  Vol.  XXXI,  p.  360. 


MARSDEN    HANSON  51 

warming  of  both  continents  and  oceans  marks  a  decided  amelioration 
of  climates  since  the  culmination  of  The  Ice  Age,  or  a  warming  earth. 
The  chill  of  this  glacial  period  extended  over  the  entire  globe,  con- 
tinents as  well  as  oceans — it  was  severest  in  middle  latitudes,  notably 
in  the  Northern  Hemisphere,  where  there  were  land  areas  to  receive 
it,  and  affected  tropical  and  torrid  latitudes  by  the  lowering  of  the 
snow  line  at  least  several  thousand  feet,  and  for  the  first  time  the 
two  curves  of  land  and  ocean  temperatures  reached  the  inferior 
limit  practically  concurrently,  all  other  continental  depressions  of 
moment  causing  intersections  with  the  ocean  temperature  curve. 

THESE  PHENOMENA  MARK  THE  GLACIAL  PERIOD  OF  PLEISTOCENE 
TIME,  OR  THE  ICE  AGE,  AS  THE  CLIMACTERIC  PERIOD  OF  THE  GEOLOGIC 
HISTORY  OF  THE  EARTH. 

In  which  Age  solar  control  of  surface  temperatures,  inaugurated 
in  Permo-Carboniferous  time  in  tropical  latitudes,  was  finally  ef- 
fected, and  earth  heat  ceased  to  be  a  sensible  factor  in  climatic  con- 
trol. The  fluctuating  climates  incident  to  this  local  factor  passed  into 
geologic  history  and  glaciation  ceased  to  be  a  recurrent  or  a  probable 
progressive  condition,  and  the  earth  became  a  heatgathering  or  warm- 
ing body. 

THE  PERIODS  OF  MOUNTAIN  MAKING  OR  OF  "  CHANGES  IN  THE  TOPO- 
GRAPHIC    FORM     OF    THE     EARTH'S     SURFACE  " 

Nearly  or  quite  coincident  with  each  period  of  sharp  depression 
and  rise  in  the  curve  of  continental  temperatures  there  is  a  period 
of  crustal  adjustment  and  rupture,  except  in  the  latter  part  of  the  rise 
in  temperature  now  in  progress  and  as  noted  in  slow  glacial  retreat 
and  the  corresponding  advance  in  life.  There  were  other  adjust- 
ments which  do  not  appear  to  have  been  accompanied  by  such  marked 
temperature  changes,  but  these  are  less  in  number.  The  connection 
between  these  changes  in  temperature  and  crustal  rupture  is  three- 
fold— First,  the  long  interval  of  stability  preceding  each  permitted 
continents  to  cool  and  be  partly  loaded  by  glaciation ;  second,  this 
glaciation  disturbed  the  isostasy  of  the  forming  crust  and  caused 
conformable  adjustments ;  and  finally,  the  heat  thus  liberated  tended 
to  restore  continental  temperatures  and  the  stored  heat  of  the  oceans. 
During  the  two  periods  of  maximum  glaciation,  these  readjustments 
seem  to  have  been  repeated  and  were  accompanied  by  several  short 
epochs  of  deglaciation  and  reglaciation.1 

In  these,  consequent  actions  and  reactions  is  manifestly  offered, 
an  answer  to  Professor  Schuchert's  question  :  "  What  is  it  that  forces 

JThe  Great  Ice  Age,  Professor  J.  Geikie,  p.  790,  (ed.  1894). 


52  THE   EVOLUTION    OF    CLIMATES 

the  earth's  topography  to  change  with  varying  intensity  at  irregularly 
rhythmic  intervals  "  ? x 

There  were  doubtless  other  causes,  but  non-uniform  glacial  over- 
loadings  and  the  restorations  of  these  loads  uniformly  distributed 
over  the  ocean  bottoms  must  have  imposed  serious  disturbances  to 
isostasy ;  these  made  themselves  manifest  at  the  close  of  each  period 
of  crustal  stability  which  preceded  the  several  glaciations. 

From  the  earliest  Proterozoic  to  the  close  of  Pleistocene  time  Pro- 
fessor Schuchert  notes  thirteen  (13)  periods  of  depression  of  con- 
tinental temperatures  and  one  of  ocean  temperatures.  These  have 
been  previously  recited  and  are  indicated  on  the  diagram. 

Two  of  the  glaciations  accompanying  these  depressions  were  of 
notable  extent  and  severity  and  were  distinctly  zonal  in  their  occur- 
rence and  maxima;  they  were  also  characterized  by  Interglacial 
epochs,  and  by  the  escape  of  the  latitudes  glaciated  in  one  during  the 
glaciation  of  the  other.  The  first  was  Permo-Carboniferous  and  the 
latter  Pleistocene  glaciation. 

All  of  the  other  depression  of  continental  temperatures  do  not 
appear  to  have  been  accompanied  by  glaciation — at  least  of  marked 
extent,  but  most  of  them  recorded  their  occurrence  by  deposits  of 
tillite  in  various  latitudes,  so  that  there  can  be  little  doubt  of  the  ac- 
tion of  ice  over  considerable  areas. 

The  two  zonal  glaciations  were  of  such  striking  characteristics  and 
significance  that  they  will  be  considered  separately  ;  the  occurrence  of 
interglacial  epochs  were  incidents  common  to  both,  and  their  sim- 
ilarity was  manifestly  imposed  by  similar  causes  and  conditions  acting 
at  widely  separated  periods  and  latitudes,  and  marked  alternations  of 
conditions  first  favorable  to  glaciation  and  then  to  deglaciation  before 
finally  yielding  to  the  latter. 

The  non-zonal  or  minor  glaciations,  if  we  may  call  them  such,  oc- 
curred both  before  and  after  Permo-Carboniferous  glaciation  and 
there  were  no  especial  features  nor  conditions  differentiating  one 
from  the  other.  They  range  in  time  from  the  earliest  to  the  latest 
era,  in  latitude  throughout  the  temperate,  tropical  and  torrid  zones 
of  today,  possibly  into  the  polar. 

Applying  the  principles  herein  advocated  these  depressions  in  con- 
tinental temperatures  were  caused  by  the  failure  of  earth  heat  to 
maintain  the  temperature  of  continents  above  freezing  during  the 
intervals  between  the  ruptures  noted  on  the  diagram,  which  from 
time  to  time  made  increments  of  earth  heat  available  as  climatic 

1L.  c.  p.  311.     Carnegie  Institution,  Pub.  192,  p.  298. 


f 


MARSDEN    MANSON  53 


factors,  and  restored  more  genial  conditions  inside  the  cloud-sphere, 
and  replenished  the  stored  heat  of  the  still  warm  but  slowly  cooling 
oceans.  Each  of  these  glaciations  recorded  the  fact  that  solar  energy 
was  not  available  to  prevent  it  although  in  latitudes  which  would  have 
been  exposed  to  its  power  unless  intercepted  by  an  effective  agent — 
for  there  is  a  significant  absence  of  any  evidence  which  would  show 
entire  solar  control  of  the  temperature  and  ice  distributions  during 
any  of  the  eras  prior  to  the  present,  except  those  solar  influences 
which  manifestly  imposed  a  zonal  distribution  of  ice  in  Permo- 
Carboniferous  and  Pleistocene  glaciations,  without  being  able  to 
prevent  their  occurrence  in  latitudes  which  could  not  have  been  glaci- 
ated under  exposure  to  its  heating  effects ;  and,  in  the  deglaciations 
of  these  latitudes.  In  this  respect  all  glaciations,  even  the  short 
period  reglaciations  following  interglacial  epochs,  distinctly  record 
the  fact  that  they  were  independent  of  direct  solar  heat  control  and 
not  ascribable  to  variations  in  solar  energy,  by  reason  of  the  contra- 
dictions and  anomalies  involved  in  any  assumption  or  hypothesis 
assuming  or  predicating  such  control. 

In  all  particulars  both  the  non-zonal,  minor  glaciations  and  the 
greater  zonal  glaciations  and  accompanying  interglacial  epochs  con- 
tradict any  assumption  of  solar  control.  They  however  answer  and 
agree  in  every  particular  as  phenomena  occurring  inside  a  constant  tem- 
perature chamber  of  moist  air  and  clouds,  practically  impenetrable  to 
radiations  from  either  source  of  heat  and  enclosing  a  globe  with  sur- 
faces of  different  specific  heat  which  were  both  dependent  upon  the 
interior  supply — which  was  not  only  intermittently  made  available 
and  slowly  lost  through  the  walls  of  moist  air  and  clouds,  but  con- 
served in  the  fields  of  its  actual  loss  in  the  outer  atmosphere  by  the 
practically  constant  and  far  more  powerful  source,  solar  energy. 

As  the  more  quickly  cooling,  lighter  and  weaker  portions  of  the 
crust  and  the  atmosphere  lost  their  heat,  exposed  areas  in  any 
latitude  were  glaciated  and  the  materials  composing  tillite  were 
shifted  by  glacial  erosion  and  flow,  until  the  isostasy  thus  disturbed 
and  the  resistance  of  the  crust  being  overcome  its  rupture  followed 
with  the  consequent  liberation  of  the  interior  heat  supply,  accelera- 
tion of  denudation  and  exposures  of  radio-active  materials.  The 
repetition  of  these  reactions  is  recorded  at  the  close  of  long  periods 
of  crustal  stability  by  the  coincident  occurrence  of  glaciations  closely 
followed  by  a  general  increase  in  temperature,  due  to  the  setting  free 
of  increments  of  earth  heat. 

There  were  specific  conditions  imposing  more  severe  glaciations 
along  zonal  lines,  first  in  the  tropical  and  later  in  the  temperate  lati- 

f 


54  THE   EVOLUTION    OF    CLIMATES 

tudes  of  today,  with  accompanying  interglacial  epochs  which  must  be 
dealt  with  under  separate  headings,  although  their  prime  causes  were 
the  same — a  failure  of  earth  heat  inside  the  constant  temperature 
chamber.  But  in  the  cases  of  interglacial  epochs,  these  failures  were 
complicated  with  the  cooling  of  the  oceans  to  certain  critical  temper- 
atures which  must  be  fully  considered. 

A  COOLING  AND  A   WARMING  EARTH 

Professor  Schuchert's  perplexity,  "  Further  a  cooling  earth  is  yet 
to  be  demonstrated."  *  appears  to  be  demonstrated  by  the  Geologic 
record  of  climates  which  registers  first  a  cooling  and  later  a  warming 
earth. 

A   CODLING   EARTH 

A  cooling  earth  during  long  eras  of  fluctuating  continental  temper- 
atures, varying  inside  its  heat  retaining  and  protecting  walls  of  moist 
air  and  clouds  between  approximate  limits  of  50°  and  minus  5°  Cent. 

During  these  eras  the  heat  held  in  the  non-conducting  and  forming 
crust  was  slowly  and  intermittently  liberated  so  that  the  worked  over 
materials  which  at  one  time  or  another  were  in  contact  with  water, 
probably  measure  scores  of  miles  in  thickness.  This  heat,  conserved 
by  effective  processes  imposed  by  itself  through  water  in  its  various 
forms,  and  under  partial  replacement  from  solar  radiation  in  the 
fields  of  its  actual  loss,  has  performed  nearly  all  the  work  recorded 
during  geologic  climates. 

Cooling  oceans  record  a  loss  of  heat  more  slowly  and  within  fluc- 
tuations of  narrower  limits ;  but  none  the  less  wide  and  effective 
when  the  extreme  temperatures  of  Proterozoic  or  early  Paleozoic 
oceans  are  compared  with  Pleistocene  and  modern  oceans.  The 
former  were  tropical  and  warm  temperate  and  no  colder  in  their 
deeps  than  the  coldest  surface  temperatures.  The  latter  are,  with  the 
exception  of  the  surfaces  of  temperate,  tropical  and  equatorial  oceans, 
still  near  the  freezing  point  of  water,  or  at  the  temperature  of  polar 
oceans. 

The  successive  cooling  of  continents  as  the  forming  crust  lost  its 
heat  is  recorded  in  several  minor  and  two  major  glaciations.  The 
glaciation  between  latitudes  15°  to  35°  north  and  south  and  the  sub- 
sequent glaciation  of  middle  and  high  latitudes  brought  the  greater 
portion  of  the  land  surfaces  into  contact  with  ice.  The  final  chilling 
of  the  oceans  brought  over  70  per  cent  of  the  crust  into  contact  with 
water  at  its  minimum  temperature,  which  with  polar  oceans  and  con- 
tinents yet  remain  at  about  4°  Cent. 

1  Report  Smithsonian  Institution  1914,  p.  311. 


MARSDEN    HANSON  55 

Thus  nearly  the  entire  surface  of  the  lithosphere  has  been  brought 
into  contact  with  ice  or  with  water  at  its  lowest  temperature  and 
about  80  per  cent  is  yet  at  this  temperature.1 

A  WARMING  EARTH 

Professor  Schuchert  did  not  extend  his  continental  temperature 
curve  into  the  Modern  Era  so  as  to  note  the  amelioration  of  surface 
temperatures  which  solar  radiation  has  wrought  since  the  vast  gla- 
ciations  of  the  Ice  Age.  The  same  energy  and  conditions  which 
brought  the  deglaciations  recorded  since  Pleistocene  time  are  yet 
active  and  their  effects  are  yet  cumulative.2  A  cooling,  and,  later  a 
warming  earth  could  not  be  more  clearly  recorded  nor  more  impres- 
sively demonstrated. 

This  rewarming  was  inaugurated  by  a  new  control  which  itself 
provides  a  moderate  limit  against  excessive  heating,  under  this  new 
control  have  been  and  are  being  developed  higher,  nobler  types  of 
life,  at  the  head  of  which  stands  the  human  race. 

PERMO-CARBONIFEROUS    AND    PLEISTOCENE    GLACIATIONS    AND    INTER- 
GLACIAL   EPOCHS 

There  are,  therefore  three  important  and  notable  chapters  in  geo- 
logic history  which  demand  attention  not  only  by  reason  of  their 
analogies  and  apparent  anomalies,  but  because  they  furnish  crucial 
tests  of  any  explanation  or  interpretation  of  the  causes  and  conditions 
which  controlled  geologic  climates  and  the  period  during  which  they 
"  merged  without  abrupt  change  "  into  those  of  the  Modern  Era. 

These  chapters  are: 

(1)  Permo-Carboniferous  Glaciation. 

(2)  Pleistocene  Glaciation. 

(3)  The  Inter-glacial  Epochs. 

PERMO-CARBONIFEROUS    GLACIATION 

This  glaciation  was  distinct  in  locality,  extent  and  occurrence.  "  It 
lies  in  the  midst  of  geologic  history  with  periods  of  great  uniformity 
and  remarkable  polar  geniality  both  before  and  after  it."  5 

1  The  author  has  not  had  an  opportunity  to  observe  extended  areas  within  the 
torrid  zone ;  but  the  topographic  forms  and  physiographic  features  described  by 
others  indicate  to  him,  and  he  has  expressed  the  probability,  that  continental 
areas  under  the  equatorial  cloud-belt  were  glaciated  in  Pleistocene  time. 

2  Science,  N.  S.,  Vol.  47,  No.  1200,  pp.  639-640,  and  authorities  there  quoted 
or  referred  to ;  ib.  Vol.  XLVII,  No.  1220,  pp.  487-488. 

3  Geology,  Chamberlin  and  Salisbury,  Vol.  II,  p.  656. 


56  THE   EVOLUTION    OF    CLIMATES 

The  glaciations  of  this  period  were  distributed  in  the  latitudes  of 
the  tropical  arid  zones  of  today,,  or  between  latitudes  15°  and  35° 
north  and  south.1 

No  cold  temperate  climates  of  wide  extent,  such  as  that  of  Pliocene 
time,  preceded  them,  although  a  cold  temperate  flora  was  locally  de- 
veloped adjacent  to  the  glaciations  and  gave  way  to  the  milder  forms 
of  life  of  Triassic  time.  Warm  temperate  and  tropical  life  apparently 
flourished  between  the  zones  of  glaciation  in  a  broad  equatorial  zone 
some  30  or  more  degrees' wide  and  north  polar  latitudes  were  "  fre- 
quented by  ferns,  corals,  figs  and  magnolias.2  The  data  for  determ- 
ining Antarctic  climates  of  Permo-Carboniferous  time  are  meagre, 
but  inferentially  they  were  also  temperate. 

Temperate  latitudes,  which  later  in  Pleistocene  time  were  deeply 
glaciated,  also  escaped  in  the  period  of  maximum  glaciation  of  trop- 
ical latitudes. 

There  are  therefore  presented  in  Permo-Carboniferous  time  zonal 
glaciations,  deglaciations  and  reglaciations  in  latitudes  which  could 
not  have  been  glaciated  under  direct  solar  control;  the  absence  of 
complete  solar  control  is  made  manifest  by  the  fact  that  polar  and 
middle  latitudes  which,  under  such  control  should  have  also  been 
glaciated  remained  mild.  Repeated  partial  deglaciations  and  regla- 
ciations of  tropical  latitudes,  assumed  to  have  been  under  solar 
energy,  are  recorded,  but  without  evidence  of  a  zonal  arrangement' 
of  climates  ;  these  conditions  merged  into  the  universally  mild  climate 
of  the  Triassic,  such  as  that  which  in  Carboniferous  time,  preceded 
these  glaciations — an  admittedly  complex  set  of  conditions,  not  ex- 
plicable under  solar  control,  and  not  possible  of  assignment  entirely 
to  earth  heat  control. 

Of  these  conditions  Profs.  Chamberlin  and  Salisbury  remark : 

Between  a  marvelous  deployment  of  glaciation,  a  strangely  dispersed  deposi- 
tion of  salt  and  gypsum,  an  extraordinary  development  of  red  beds,  a  decided 
change  in  terrestrial  vegetation,  a  great  depletion  of  marine  life,  a  remarkable 
shifting  of  geographic  outlines,  and  a  pronounced  stage  of  crustal  folding,  the 
events  of  the  Permian  period  constitute  a  climateric  combination.  Each  of 
these  phenomena  brings  its  own  unsolved  questions,  while  their  combination 
presents  a  plexus  of  problems  of  unparalleled  difficulty.8 

1  Compare  plates   17  and   18  and  p.   16,  BARTHOLOMEW'S   PHYSICAL  ATLAS, 
Meteorology;  and,  Schuchert's  chart  of  early  Permic  Glaciation,  Smithsonian 
Report,  1914,  p.  281. 

2  Sir    A.    Geikie,   Geology,   Vol.    II,   p.    1081.      Chamberlin   and    Salisbury, 
Geology,  Vol.  II,  p.  677. 

3  Geology,  Vol.  II,  p.  655. 


MARSDEN    HANSON  57 

Under  the  controlling  principles  and  conditions  outlined  in  Part  I, 
the  first  regions  to  be  subjected  to  zonal  glaciation  were  the  anti- 
cyclonic  zones  of  cold  descending  winds.  Lands  in  these  zones  were 
exposed  to  glaciation  from  warm  oceans  until  they  chilled  to  that 
degree  which  impaired  the  cloud  sphere  in  the  bands  of  its  least 
density.  As  heretofore  held  this  a  critical  ocean  temperature,  readily 
fluctuating  from  increments  of  earth  heat  between  that  degree  which 
would  fail  to  sustain  or  that  which  would  restore  the  cloud  sphere. 
Each  failure  would  expose  the  surface  to  the  deglaciating  power  of 
solar  energy,  and  each  restoration  would  intercept  this  energy  and 
leave  surface  temperatures  to  the  effects  of  the  fading  supply  of  earth 
heat.  Crustal  ruptures  might  liberate  sufficient  earth  heat  to  partially 
deglaciate,  but  the  ultimate  effect  would  be  to  restore  glaciation  until 
more  slowly  cooling  oceans  again  sufficiently  lost  their  stored  portion 
of  this  increment  of  earth  heat  to  again  permit  the  clearing  of  tropical 
skies  and  reimpose  deglaciation  under  solar  energy,  and  finally  estab- 
lish its  control. 

These  phenomena  were  therefore  not  manifestations  of  short 
period  variations  of  solar  energy,  but  of  alternations  of  control  of 
surface  temperatures,  first  by  the  slow  loss  of  earth  heat  liberated 
by  crustal  ruptures,  etc.,  and  then  by  solar  energy  admitted  to  the 
surface  by  failures  in  the  continuity  of  the  cloud  sphere.  In  these 
climatic  complications  are  presented  the  dual  and  the  alternate  effects 
of  the  two  sources  of  heat.  The  one  being  gradually  exhausted  and 
put  into  temporary  effect  through  crustal  ruptures,  denudations,  ex- 
posures of  radio-active  materials,  chemical  and  physical  actions  and 
reactions  etc.,  the  other,  a  practically  constant  source,  intermittently 
and  finally  permanently  admitted  in  control  in  these  zones  of  least 
cloudiness,  by  temporary  and  later  final  failure  of  the  cloud  sphere 
in  these  latitudes.  They  have  not  since  been  subjected  to  severe 
glaciation,  although  the  final  chill  of  the  oceans  in  the  subsequent 
Ice  Age  of  Pleistocene  time  may  have  extensively  lowered  the  snow 
line  in  tropical  and  equatorial  latitudes.  Partial  and  later  final  de- 
glaciation of  tropical  latitudes  is  therefore  recorded  in  the  phenomena 
of  Permo-Carboniferous  glaciation  and  deglaciation  as  recited  by 
Professor  Schuchert. 

CLIMATIC    CONDITIONS    BETWEEN     PERMO-CARBONIFEROUS     AND     PLEISTOCENE    TIME 

Following  this  period  of  maximum  glaciation  in  tropical  lati- 
tudes and  up  to  the  succeeding  one  in  temperate  and  polar  lati- 
tudes there  lies  a  group  of  periods  embracing  fluctuating  climates; 
these  were  principally  tropical  and  warm  temperate  of  wide  distri- 


5  THE   EVOLUTION    OF    CLIMATES 

bution,  but  broken  by  short  glaciations  of  less  marked  extent  than 
the  others ;  and  closed  with  the  widely  distributed  cold  temperate 
climate  of  Pliocene  time. 

The  oceans,  throughout  these  periods,  remained  tropical  or  tem- 
perate until  the  Pliocene  and  early  Pleistocene  when  cold  temperate 
oceans  succeeded. 

As  in  the  minor  glaciations  prior  to  Permo-Carboniferous  time  so 
on  elevated  regions,  on  the  interiors  of  continents,  where  cold  air 
could  descend  to  the  quickly  cooling  land  and  on  the  easterly  shores 
of  continents  minor  glaciations  occurred.  These  were  similar  to 
those  preceding  Permo-Carboniferous,  with  the  restriction  that  they 
were  not  so  common  in  tropical  latitudes,  as  these  apparently  -re- 
mained under  solar  control. 

PLEISTOCENE  GLACIATION 

This,  the  last  and  widest  glaciation  in  latitudinal  effects  reached  its 
maxima  in  temperate  and  polar  latitudes.  Its  greatest  deployment 
was  under  the  widest  extent  of  continental  areas  between  latitudes 
40°  and  60°  North.  Corresponding  land  areas  in  the  southern  hem- 
isphere were  also  deeply  glaciated  but  their  extent  was  restricted  by 
the  limited  areas  of  the  southerly  part  of  South  America,  South 
Australia,  Kerguelen,  New  Zealand,  and  smaller  islands.  These 
glaciations  were  under  the  temperate  rain  belts  of  the  Modern  Era. 

The  zones  from  which  glacial  dispersion  took  place  in  the  widest 
land  extents  under  the  north  temperate  rain  belt  were  not  the 
mountain  divides,  but  a  line  of  maximum  precipitation  which  cor- 
responds with  the  track  of  maximum  storm  frequency  of  the 
present  era.1 

From  this  belt  glacial  dispersion,  modified  by  orographic  features, 
appears  to  have  reached  latitude  38°  in  the  valley  of  the  Mississippi, 
latitude  65°  in  that  of  the  MacKenzie,  latitude  48°  in  that  of  the 
Volga,  and  into  the  Arctic  Ocean  and  the  White  Sea. 

Polar  latitudes,  which  escaped  in  the  Permo-Carboniferous,  were 
deeply  glaciated  for  the  first  time  in  Pleistocene  time.  Their  maxima 
were  reached  probably  later  than  those  of  temperate  latitudes  and 
deglaciation  has  and  is  proceeding  more  slowly,  as  they  are  least  ex- 
posed to  solar  radiation  and  yet  remain  deeply  glaciated.  Deglacia- 
tion is,  however,  progressing  under  solar  control  in  both  Arctic  and 
Antarctic  regions,  which,  taken  in  connection  with  the  corresponding 

1  See  Plates  28  and  29,  Bartholomew's  Physical  Atlas,  Vol.  III. 


MARSDEN    MANSON  59 

deglaciation  of  temperate  latitudes,  calls  for  ultimate  and  correspond- 
ing deglaciation  of  polar  regions.1 

Oceans  for  the  first  time  in  geologic  history  reached  glacial  tem- 
peratures in  middle  and  polar  latitudes — but  such  low  temperatures 
do  not  appear  to  have  been  imposed  upon  oceans  in  tropical  latitudes, 
as  these  shared  in  the  ameliorating  influences  of  solar  energy,  which 
reached  these  latitudes  after  the  oceans  fell  to  that  temperature  which 
depleted  cloudiness  in  these  anti^cyclonic  zones  of  least  cloudiness. 

Glaciation  was  therefore  more  extended  in  Pleistocene  time  than 
at  any  other  period  of  geologic  history.2 

These  conditions  "  shaded  without  abrupt  change  of  any  kind  into 
what  is  termed  the  Human  or  Recent  Period."  (Geikie). 

There  is  therefore  presented  in  the  glacial  phenomena  of  the  Pleis- 
tocene period,  or  Ice  Age,  the  culmination  of  a  series  of  remarkable 
climatic  phenomena  merging  into  present  conditions  after  two  widely 
separated  periods  of  zonal  glaciations,  and  of  periods  of  minor  gla- 
ciations,  all  laid  down  unconformably  to  the  climates  into  which  they 
have  shaded  and  which  are  distinctly  under  solar  control. 

INTER-GLACIAL  EPOCHS 

The  merging  of  one  condition  into  the  other  was  accomplished 
through  a  remarkable  series  of  minor  changes  from  conditions  favor- 
able to  glaciation  into  those  unfavorable  thereto,  characterized  as 
inter-glacial  epochs.  Of  these  and  their  causes  Professor  Schuchert 
remarks,  "  The  causation  for  the  warmer  interglacial  climates  is  the 
most  difficult  of  all  to  explain,  and  it  is  here  that  factors  other  than 
those  mentioned  may  enter."' 

The  explanation  which  the  writer  offers  for  these  complicated 
conditions  involves  three  factors : 

1 i )  Solar  Energy,  to  which  the  earth,  whatever  its  conditions,  has 
been  exposed  throughout  its  cosmic  existence,  and  which  has  been 
nearly  constant,  so  far  as  our  knowledge  goes,  during  geologic  time. 

(2)  Earth  Heat,  locked  during  geologic  time  in  a  practically  non- 
conducting crust  from  which  it  has  been  released  by  the  various  pro- 

1  Science  N.  S.  Vol.  XLVI,  No.  1200,  pp.  639-640,  Dec.  28,  1917.  Proc.  loth 
Session  International  Geol.  Congress,  Mexico,  1906,  \b.,  nth  Session  Stockholm, 
1910,  p.  1 102. 

a "  The  distinguishing  feature  of  the  Pleistocene  period  is  its  phenomenal 
glaciation." 

Chamberlin  and  Salisbury,  Geology,  Vol.  Ill,  p.  327. 

"  The  whole  world  felt  its  effects."    Ib. 

*L.  c.  p.  311. 


60'  THE    EVOLUTION    OF    CLIMATES 

cesses  of  rupture,  denudation,  the  exposure  and  transformation  of 
radio-active  substances,  volcanism,  etc. 

(3)  The  conditions  under  which  these  two  sources  of  heat  have 
acted,  and  which  were  imposed  through  the  functions  of  moist  air 
clouds  and  warm  oceans,  these  shut  in  the  interior  supply  as  liberated 
from  the  forming  and  non-conducting  crust,  inside  a  constant  temper- 
ature chamber  of  moist  air  clouds  and  outer  media,  into  which  was 
brought  into  available  use  the  several  increments  of  earth  heat  as 
freed  by  various  processes,  here  it  acted  as  the  controlling  tempera- 
ture factor  in  whole  or  in  part  until  its  final  loss  was  recorded  by 
glacial  ocean.  Upon  the  outside  of  these  walls  solar  energy  wrought 
its  constant  effects  and  was  zonally  admitted  first  in  the  bands  of 
least  cloudiness  and  later  in  those  of  greater  cloud  density,  each  zone 
being  subjected  to  a  fluctuating  admittance  of  this  source  of  energy 
by  reason  of  slight  fluctuations  in  ocean  temperatures  when  at  critical 
stages  in  the  generation  of  sufficient  or  insufficient  water  vapor  to 
maintain  cloudiness  in  the  zones  of  its  varying  densities.1 

The  author  realizes  that  he  may  have  somewhat  broadened  the 
masterly  presentations  of  Professor  Schuchert  and  that  his  record 
of  geologic  facts  has  been  prepared  under  conceptions  of  the  control 
of  geologic  climates  totally  different  from  that  herein  presented.  It 
is  hoped,  however,  that  the  reasons  for  this  radical  difference  as  given 
in  Parts  I  and  II  are  justified  upon  the  basis  therein  recited ;  and,  that 
the  marvelous  records  of  geologic  climates  and  their  gradual  change 
into  those  of  the  present  will  be  found  to  fit  into  the  present  interpre- 
tation better  than  they  have  into  the  assumption  of  solar  control. 

1  These  changes  have  been  discussed  on  pp.  33  et  seq.,  39  ct  seq.  and  46.  Tt 
is  not  necessary  to  repeat  the  views  there  expressed. 


PART  III 

RECAPITULATION  OF  CONCLUSIONS  AND  THEIR  GENERAL 
APPLICATION 

SUMMARY  OF  CONCLUSIONS 

These  studies  have  resulted  in  the  conclusion  that  a  logical  applica- 
tion of  the  known  principles  of  atmospheric  physics ;  of  the  heat  con- 
serving functions  of  water  in  its  various  forms  and  their  action  upon 
radiant  energy,  the  intermittent  liberation  of  heat  from  the  non- 
conducting crust  by  ruptures  and  its  exposure  to  denudation  and  to 
the  setting  free  of  radio-active  energies,  together  with  the  further 
conservation  of  this  heat  through  the  utilization  of  solar  energy  in 
and  beyond  "  the  true  radiating  surface  "  of  the  planet  are  competent 
to  explain  the  variations  and  developments  of  geologic  and  present 
climates  without  resort  to  assumptions  or  "  working  hypotheses  "  of 
any  kind ;  and,  that  all  climatic  phenomena  come  within  reasonable 
explanation  upon  the  rejection  of  the  assumption  of  solar  climatic 
control  prior  to  that  era  during  which  this  control  is  distinctly  de- 
marked  in  zones  of  climate. 

These  conclusions  are  so  radically  at  variance  with  those  reached 
by  all  others  who  have  essayed  these  problems  that  it  may  be  well  to 
specifically  recapitulate  these  conclusions. 

1.  The  assumption  that  solar  control  alone  prevailed  during  any 
period  of  geologic  time  is  rejected.    The  basis  of  this  rejection  is,  the 
complete  failure  of  any  and  all  attempts  to  fit  the  facts  of  geology 
thereto  and  the  contradictions  and  anomalies  which  this  control  can- 
not meet.    This  carries  with  it  the  rejection  of  mathematical  calcula- 
tions limiting  the  time  and  effects  of  earth  heat  influences,  which  are 
used  to  fortify  the  assumption  of  solar  control.    The  basis  of  the 
rejection  of  these  results  is  the  inadequateness  of  the  assumed  factors 
and  the  omission  of  the  larger  and  more  important  ones,  which  con- 
trolled the  conservation  of  earth  heat ;  and  also,  because  these  calcu- 
lations were  made  before  the  sources  of  heat  rendered  available  by 
the   exposure   and   transformation   of    radio-active   materials   were 
discovered. 

2.  It  is  held  that  this  heat,  conserved  by  a  non-conducting  crust, 
stored  in  the  oceans  and  liberated  as  a  climatic  factor  by  slow  denu- 
dations and  exposures  of  radio-active  materials,  by  faults,  fractures, 

61 


62  THE   EVOLUTION    OF    CLIMATES 

ruptures,  volcanism,  and  other  changes  of  its  topographic  forms,  was 
a  factor  in  temperature  conditions  until  the  exhaustion  of  its  last 
effective  increments  from  the  oceans  in  Pleistocene  time. 

3.  That  the  supply  of  ocean  stored  heat  replenished  from  time  to 
time  by  the  above  processes  kept  the  oceans  warm  until  near  the  close 
of  geologic  climates  as  attested  by  the  character  and  distribution  of 
fossil  marine  life  by  the  distribution  of  temperatures  and  of  ice ;  they 
fluctuated  through  very  moderate  limits  and  fell  to  glacial  temper- 
atures only  in  Pleistocene  time. 

4.  That  oceans  at  these  temperatures  do  not  generate  sufficient 
water  vapor  to  maintain  more  than  the  present  52  per  cent  of  cloudi- 
ness which  admits  solar  energy  to  the  lower  and  denser  strata  of  the 
atmosphere  and  to  the  surface,  which  it  warms.     The  earth  then 
emits  long  wave  length  radiations  which  are  trapped  or  absorbed  in 
the  atmosphere.     This  process,  within  certain  reasonable  limits  is 
cumulative,  and  results  in  a  gradual  amelioration  of  the  conditions 
of  Pleistocene  time. 

The  oceans  at  the  higher  temperatures  of  pre-Pleistocene  time 
maintained  a  far  denser  and  more  continuous  cloudiness,,  which  shut 
in  earth  heat  and  intercepted  and  utilized  solar  energy  in  the  upper 
atmosphere  as  a  further  conservative  influence. 

5.  That  the  interposition  of  this  cloud  sphere  imposed  two  highly 
conservative  conditions  upon  the  further  conservation  of  earth  heat : 
(a)  The  moist  air  and  clouds  are  practically  impenetrable  to  the  radia- 
tions emitted  by  the  planetary  surface,  and  the  loss  of  this  heat 
through  these  media  was  restricted  to  the  interchange  of  water  in  its 
various  forms  in  the  atmosphere  and  of  the  action  of  cyclonic  and 
anti-cyclonic  circulation  as  fixed  by  solar  radiation ;  (b)  solar  radia- 
tion as  a  source  of  heat  was  restricted  to  the  part  of  a  conservator  of 
earth  heat  by  its  absorption  and  utilization  upon  and  above  the  cloud 
sphere,  and  was  admitted  to  the  lower  regions  of  the  atmosphere  and 
to  the  planetary  surface  as  a  controlling  factor  by  reason  of  impair- 
ments in  the  cloud  sphere. 

6.  That  continents  thus  protected  from  solar  radiation,  and  by 
reason  of  low  specific  heat  and  elevation  frequently  reached  glacial 
temperatures  during  the  intervals  between  outbursts  of  earth  heat 
from  the  forming  crust,  during  which  intervals  adequate  earth  heat 
was  not  available  to  prevent  glaciation,  nor  was  solar  radiation  avail- 
able by  reason,  of  the  intercepting  cloud  sphere.     They  were  also 
exposed  under  the  same  condition  to  two  periods  of  maximum  glaci- 
ation, first  in  the  regions  of  cold  downcast  currents  of  anti-cyclonic 


j         MARSDEN    MANSON  63 

latitudes,  and  later  to  the  chill  of  final  refrigeration  in  Pleistocene 
time. 

7.  That  during  geologic  time,  as  now,  the  functions  of  solar  radia- 
tion prevailed  in  fixing  zones  or  belts  of  cyclonic  and  anti-cyclonic 
circulation,  of  maximum  and  minimum  barometric  pressure  of  con- 
sequent cloud  densities  and  belts  of  maximum  and  minimum  pre- 
cipitation, but  its  heating  or  temperature  effects  were  intercepted  by 
clouds  maintained  by  warm  oceans  and  the  available  supply  of  earth 
heat  inside  the  constant  temperature  chamber  of  moist  air  and  clouds. 
Under  these  conditions  the  supply  of  water  vapor  was  dependent 
upon  the  stored  heat  of  the  oceans  and  its  disposition  as  a  circulating 
agent  in  the  form  of  vapor,  clouds,  rain  and  snow  was  fixed  by  solar 
radiation  acting  on  the  spheroid  of  air  and  clouds,  these  effects  in  no 
material  way  differing  from  the  present  dispositions,  except  more 
uniformity  in  the  exposed  surface  than  at  present  offered  by  land  and 
sea  and  variability  in  clouded  areas. 

8.  That  upon  the  acquisition  of  a  stable  crust  by  the  slow  processes 
of  cooling,  and,  by  the  overloading  of  continents  at  various  periods 
with  glacial  ice  and  the  removal  of  these  overloads  under  the  effects 
of  solar  energy  the  liberation  of  increments  of  heat  ceased,  and  the 
oceans  chilled  to  their  point  of  maximum  density.    This  degree  is  too 
low  to  generate  sufficient  water  vapor  to  maintain  continuous  cloud 
density  at  any  latitude,  and  leaves  surface  temperatures  under  the 
control  of  solar  radiation.    Under  this  control  glaciation  is  not  pos- 
sible until  this  source  of  energy  shall  decline  to  an  effectiveness  less 
than  that  now  reaching  polar  latitudes.     That  should  this  period 
arrive  a  type  of  glaciation  not  yet  recorded  would  follow. 

9.  Under  the  rewarming  effects  of  solar  energy  temperatures  must 
continue  to  rise  until  the  surface  of  oceans  shall  rewarm  to  a  degree 
which  will  increase  evaporation  therefrom  and  impose  a  check  to 
farther  rise  in  temperatures  by  increased  cloud  extension  and  density. 

POSSIBILITY  OF  FUTURE  GLACIATIONS 

Within  the  field  of  speculative  cosmology  future  glaciations  of  the 
earth  are  possible  from  two  causes : 

(i)  In  the  progress  of  stellar  evolution,  at  some  remote  eon  of 
time  solar  energy  may  decline  to  a  maximum  efficiency  less  than  that 
now  deglaciating  polar  latitudes  and  less  than  that  now  seasonally 
melting  off  the  polar  snow  caps  of  Mars.  The  ensuing  glaciation 
would  be  unlike  any  yet  recorded — it  would  be  inaugurated  in  polar 


64  THE   EVOLUTION    OF    CLIMATES 

latitudes  and  it  would  be  light,  since  cold  and  freezing  oceans  do 
not  yield  sufficient  water  vapor  for  severe  glaciations. 

(2)  A  cataclysmic  rupture  of  the  crust  which  would  liberate  suffi- 
cient earth  heat,  now  locked  within  its  non-conducting  crust,  to  re- 
warm  the  oceans.  This  would  re-inaugurate  geologic  climates  and 
the  ultimate  chilling  of  land  masses  with  still  warm  oceans  and  re- 
sultant dense  clouds  would  give  a  corresponding  series  of  climatic 
events  to  that  recorded  within  the  reach  of  the  geologist. 

It  is  not  improbable  that  such  phenomena  may  have  characterized 
pre-geologic  eras ;  and  that  the  eras  of  geologic  history  are  only  the 
last  chapters  of  the  formation  of  the  fully  tested  and  stable  crust. 

Under  neither  of  the  above  possibilities  may  future  glaciation  be 
regarded  as  an  impending  event. 

APPLICATION   OF   CONCLUSIONS 

As  stated  in  the  Preface,  the  object  of  this  work  is  to  offer  an  in- 
terpretation of  the  causes,  conditions  and  controlling  principles  of  the 
climates  which  the  earth  has  manifestly  undergone  during  geologic 
and  present  time. 

It  was  indicated  that  the  conclusions  would  be  applied  to  the  anal- 
ogies apparently  offered  by  other  planets.  Such  application  can  now 
be  made  only  under  a  broad  interpretation  of  the  features  presented 
by  the  planets  which  are  selected  for  this  purpose. 

If  the  principles  herein  used  for  the  interpretation  of  the  climates 
of  the  earth  have  been  rightly  selected  and  applied  and  the  conclusion 
correctly  reached  and  found  to  fit  the  geologic  record  and  present 
conditions,  these  conclusions  have  certain  general  applications  to  the 
other  members  of  our  system.  This  is  brought  out  in  the  quotations 
from  Herschel,  Chamberlin  and  Salisbury,  Barnard  and  Campbell. 

During  the  greater  part  of  geologic  time,  it  is  held  that  the  earth 
was  swathed  in  clouds  ranged  in  zones  parallel  with  the  equator. 
This  cloud  sphere  was  practically  continuous  and  presented  a  surface 
of  high  albedo — that  of  clouds,  or  about  .60.  At  present  this  surface 
is  broken  and  the  albedo  has  been  lowered  by  the  exposure  of  about 
48  per  cent  of  its  dark  surface.  Moreover,  it  is  known  that  the 
violet  end  of  the  spectrum  is  utilized  to  a  greater  extent  than  the  red 
end,  and  hence  this  end  controls  the  color  of  the  reflected  ray.1 

It  follows  that  a  planet  in  this  or  in  a  later  stage  of  climatic  devel- 
opment has  a  low  albedo,  and  the  color  of  its  reflected  light  is  that  of 

1  Hence  the  copper  red  of  the  "  earth  shine  "  on  the  new  moon,  which  reflects 
greatly  reduced  but  normal  light  from  the  crescent. 


MARSDEN    HANSON   J'    •••->.         >.-  :\  :  •5>5J- 

/ 

the  least  utilized  end  of  the  spectrum.  The  earliest  of  these  stages 
must  be  presented  by  the  larger  planets,  whose  masses  have  imposed 
a  longer  period  of  cooling  and  they  present  a  cloud-banded  surface 
of  high  albedo. 

The  latest  stage  must  have  been  reached  by  the  smaller  planets 
which,  having  cooled  more  rapidly,  have  reached  a  more  advanced 
stage  and  present  a  surface  of  low  albedo,  utilize  the  violet  end  of 
the  spectrum  and  reflect  light  deficient  in  this  color. 

The  first  stage  appears  to  be  presented  by  the  great  planet  Jupiter, 
which  seems  to  be  shrouded  in  dense  clouds  maintained  by  its  own 
heat,  and  exposes  a  surface  of  high  albedo  0.62,  with  banded  zones 
and  spots  having  varying  tangential  velocities  and  moving  freely  in 
its  atmosphere.  The  heat  emanating  therefrom  is  about  of  that  in- 
tensity which  should  be  derived  from  reflected  solar  energy.  The 
reflected  light  is  normal  and  white,  which  shows  that  neither  end  of 
the  spectrum  is  utilized  or  trapped  to  a  greater  extent  than  the  other, 
as  is  the  case  with  the  earth  and  Mars.  All  the  conditions  are  similar 
to  those  which  a  densely  clouded  earth  would  present  to  an  observer 
in  interplanetary  space. 

Mars,  on  the  other  hand,  presents  a  clear  or  slightly  cloudy  atmos- 
phere, through  which  the  features  of  the  surface  are  faintly  observed, 
notably  the  alternate  formation  and  melting  away  of  polar  snow  caps 
as  these  are  seasonally  turned  away  from  or  towards  the  sun.  The 
albedo  is  low,  only  .26,  the  violet  end  of  the  spectrum  is  manifestly 
utilized  to  a  greater  extent  than  the  red  end  and  hence  this  latter 
color  prevails  in  the  reflected  light. 

Polar  ice  caps  are  lacking  and  in  their  stead  polar  snow  fields  form 
in  winter  and  melt  off  in  summer,  foreshadowing  the  conditions  of 
the  earth's  polar  regions  when  energies  and  conditions  now  active 
shall  have  deglaciated,  first  the  north  polar  regions  in  the  land  hemis- 
phere and  later  the  ocean  bound  regions  of  Antarctica. 

Three  distinct  stages  of  climatic  evolution  are  therefore  apparently 
presented  by  these  three  planets.  Jupiter,  in  the  stage  through  which 
the  earth  has  passed ;  the  earth  in  the  stage  of  the  gradual  develop- 
ment of  solar  controlled  climates;  Mars  in  a  more  advanced  stage 
towards  which  our  present  developments  are  tending. 

If  the  eras  of  climates  through  which  the  earth  has  manifestly 
passed  and  the  changes  now  passing  before  us  have  herein  been  re- 
ferred to  their  proper  principles  and  correctly  interpreted,  the  "  in- 
tricate problems  which  have  hitherto  baffled  the  geologist "  may 
prove  grander  by  reason  of  their  simplicity  and  unity. 


(56  THE  EVOLUTION    OF   CLIMATED 

But  the  conclusions  herein  reached  traverse  those  which  are 
reached  by  able  scientists  and  which  are  taught  in  the  great  univer- 
sities. 

The  principles  upon  which  they  rest  are  believed  to  be  sound  and 
the  prime  question  is  are  these  applications  of  them  correct?  They 
will  therefore  have  to  be  judged  with  severe  caution,  attacked  and 
hammered  from  every  standpoint,  and  accepted  only  after  sound 
judgment  shall  determine  that  they  fit  and  correctly  interpret  the 
wonderful  records  in  the  crust  of  the  earth.  Aye,  more,  that  they 
yield  analogies  of  use  in  correctly  judging  the  conditions  apparently 
reached  upon  other  members  of  the  family  of  planets  to  which  the 
earth  belongs. 


THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
STAMPED  BELOW 


AN     INITIAL     FINE     OF     25     CENTS 

WILL  BE  ASSESSED  FOR  FAILURE  TO  RETURN 
THIS  BOOK  ON  THE  DATE  DUE.  THE  PENALTY 
WILL  INCREASE  TO  SO  CENTS  ON  THE  FOURTH 
DAY  AND  TO  $1.OO  ON  THE  SEVENTH  DAY 
OVERDUE. 


NOV 


29  is,.,. 


DEC  i    1933 
APR   4  t935 

SEP  18 1941 


Q 

NOV  17 1941 


Dec  10  '48DF 


LD  21-50m-8,-32 


YC 


5104 


LIBRARY  USE 

RETURN  TO  DESK  FROM  WHICH  BORROWED 

LOAN  DEPT. 

THIS  BOOK  IS  DUE  BEFORE  CLOSING  TIME 
ON  LAST  DATE  STAMPED  BELOW 


LIBRARY  USE 

MAY  291964 

L> 

Ajiwoo'r/i     r?  1>W! 

]MAY  /  'J  u4     7  \  W 

• 

T  rk  «o  A    KH     o  >«^                                    General  Library 
^E364!tl60°r94i26A                              U-««^-glif«l. 

